Recently I bumped into a problem with file-sharing - an attempt to copy files from an XP machine to a Vista computer ended up with the error "Not enough server storage". Rebooting all the computers did not help to resolve the issue. As Microsoft suggests the problem is related to a small value for IRPStackSize parameter on the server side computer.
On the server computer start Regedit.exe as Administrator, go to "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameter". From there change IRPStackSize to a value in range from 16 to 50. I made it 25 decimal (or 19 in hex). If the parameter IRPStackSize does not exit, create it as DWORD Value. Reboot the computer and check if it helps. If still not, you can try a bigger value, reboot and check again. I changed the value on all my network computers to 25 - since then the problem has not surfaced yet.