Excel 95/2000 not saving files on NW5

I am having a problem with Excel 95/2000 saving files on a Netware 5 network. It will save files alright on the C Drive but if you try to save to the network it saves the file under a temp name instead. This has happended very suddenly only to certain computers. I have tried disabling the anti-virus , but no joy. I have also tried to delete and re-create users after repairing the NDS tree, but no joy there either. Anyone got any ideas?