omv doesnt boot up if external hard drive is connected during power on!!

Hi to all, sorry if this thread isnt in appropriate section!

I have a little problem whit OMV 2.1 installed on amd64 desktop.

After installation all working fine,the system is installed on internal sata hdd, and the shared folder are locate on an external ext4 partition.
i have edited fstab file to perform automount of external drive on /media/exthdd!
My problem was born after first system restart, the PC dosnt boot and stay freeze on Manufacter (HP) logo, after some tries i understood that the problem is the external hdd, if connetted My PC dont boot up, if try to deconnect the external drive before power on all works and the system boot up fine.
Somebody have any idea for mix this issue??
Sorry for my bad lenguage, but my first language is not english

yep this is the first thing that i think, but unfortunatelly in the bios i have possibility to set CDrom drive groups and hdd drive groups for boot priority, but there arent any way to set up on the single hdd drive or single cdrom drive order, this sounds very strange for me. PC used is a bit old (like 2007), but this dont should be a problem