NFS Probs with ESX

well loaded up openmediavault
all good and easy
set a volumeup (single disk)
created a NFS share with the following extras
all_squash,insecure,async
and made it so any client can talk to it on my network
mounted in esx all good
moved a machine over for the io testing i wanted to do
all working
impressed at speed
tried to move the machine back to one of the other nfs servers on the network
esx comes back with error that it cannot create a file

now i can migrate both way with existing nfs share
so i tried to creat folders in diffrent part of the share using the esx browser to the nfs
now sometimes it works some times it does not
any one any idea
?
thanks

update
have made sure the root has the same password on both boxes
the extra options for nfs is now set to subtree_check,asyncbut still no go , allows me to map to the folder but nothing else?thanks

did full reinstall from a new download
did the same created everything and set up the nfs share
mounted in esx
migrated a server over will not move back
moved a 4 GB single iso over.... it moved back , go figure
but the machine will still not move back
i can even delete the machine by browsing in esx and deleting it
or deleting the machine from the client
any help please
thanks