Some plugins install failed when OMV behind http proxy

I deployed OMV (1.0.8 on Debian 7.6) on a system in my company lab, this system is behind a proxy, so configured $http_proxy, installation and update to 3.14 backport worked very well without any problem. But when I tried to install extplorer and virtualbox plugin, it failed, according to install log, looks like it was failed due to not able to get some files for installation.

E.g, for virtualbox installation, all packages got successfully, when setting up openmediavault-virtualbox, it required to get a file named "Oracle_VM_VirtualBox_Extension_Pack-4.3.14.vbox-extpack", but failed, tried 20 times which all are time out, finally gave up, then the installation stuck there. I have tried that below methods to retrieve this files, both OK
1. in SSH console, "wget http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack" (I have already configured $http_proxy);
2. in my desktop browser, input link of the file, browser can get it successfully;

Can anyone help me to figure out what's the difference in plugin installation script to receive the file? Thanks!
BTW, i have installed both plugin on the system in my home, no similar issue encountered, so i believe this is an issue related to http proxy, but not sure whether on OMV side or proxy server side.

Because I can't paste all installation log, I just cut the part of failed steps:
*********************************************************************************************************************

Setting up g++ (4:4.7.2-1) ...
update-alternatives: using /usr/bin/g++ to provide /usr/bin/c++ (c++) in auto mode
Setting up build-essential (11.5) ...
Setting up openmediavault-virtualbox (1.0.9.2) ...
--2014-08-18 12:45:20-- http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Resolving download.virtualbox.org (download.virtualbox.org)... 137.254.120.26
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 12:47:29-- (try: 2) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 12:49:38-- (try: 3) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 12:51:48-- (try: 4) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 12:53:59-- (try: 5) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 12:56:12-- (try: 6) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 12:58:25-- (try: 7) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:00:39-- (try: http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:02:54-- (try: 9) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:05:11-- (try:10) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:07:28-- (try:11) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:09:45-- (try:12) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:12:02-- (try:13) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:14:20-- (try:14) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:16:37-- (try:15) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:18:54-- (try:16) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:21:11-- (try:17) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:23:28-- (try:18) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:25:46-- (try:19) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Retrying.

--2014-08-18 13:28:03-- (try:20) http://download.virtualbox.org…_Pack-4.3.14.vbox-extpack
Connecting to download.virtualbox.org (download.virtualbox.org)|137.254.120.26|:80... failed: Connection timed out.
Giving up.

dpkg: error processing openmediavault-virtualbox (--configure):
subprocess installed post-installation script returned error exit status 4
Processing triggers for openmediavault ...
Restarting engine daemon ...
Errors were encountered while processing:
openmediavault-virtualbox
Creating index of upgradeable packages ...
Creating index of OpenMediaVault plugins ...

After stuck at the final installation step for a long time, i refresh the OMV main page in browser, I found "virtualbox" is still not "installed" in plugin list, but i can see it in "Services" sidebar, and also in the output of "dpkg -l | grep openmediavault"

root@omv-debian:~# dpkg -l | grep openmediavault
ii openmediavault 1.0.8 all Open network attached storage solution
ii openmediavault-anacron 1.0 all anacron plugin for OpenMediaVault.
ii openmediavault-backup 1.0.4 all backup plugin for OpenMediaVault.
rc openmediavault-extplorer 1.0.2 all OpenMediaVault eXtplorer plugin
ii openmediavault-keyring 0.3 all GnuPG archive keys of the OpenMediaVault archive
ii openmediavault-mysql 1.0.5.4 all MySQL plugin for OpenMediaVault
ii openmediavault-omvextrasorg 1.0.3 all OMV-Extras.org Package Repositories for OpenMediaVault
ii openmediavault-rsnapshot 1.0.2 all OpenMediaVault rsnapshot backup plugin.
iF openmediavault-virtualbox 1.0.9.2 all VirtualBox plugin for OpenMediaVault.

I don't what exact I did to make virtualbox plugin works, but I'm sure I haven't ran "apt-get --reinstall install openmediavault-virtualbox". Below is something I can recall, I will try another plugin-extplorer whether will work with this reinstall.

1. I retried virtualbox extension pack with "wget download.virtualbox.org/virtua…_Pack-4.3.14.vbox-extpack" to my home folder;
2. I ran "aptitude install xorg xfce4 lightdm" to install a desktop (just as a test), when set up the packages, I saw "virtualbox extension pack" was downloaded again and configured;
3. after finish step 2, log in my OMV GUI, found "VirtualBox" marked "Installed" in "Plugins", and it did works to configure datavolume, vm folder and login phpvirtualbox UI to create VM;

So i'm wondering whether there is some problem in original virtualbox plugin installation script, it didn't download package through http proxy.

I repeated the process to reproduce the issue, then executed "apt-get --reinstall install openmediavault-virtualbox", no luck, below error encountered:

root@omv-debian:~# apt-get --reinstall install openmediavault-virtualbox
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
E: Internal Error, No file name for openmediavault-virtualbox:amd64

But "apt-get install openmediavault-virtualbox" worked for me, it ran to get the correct extension pack and configured plugin successfully. The next problem is that, i found some difference between phpvirtualbox GUI and Virtualbox manager GUI in desktop, some items missed in web GUI, see below pictures, "input", "update", "extensions", "proxy" setting missed in phpvirtualbox, not sure whether is because that phpvirtualbox web service run as vbox user, not have full access.

Settings in desktop manager:

Settings in Web manager: