Office and Lotus 1-2-3 files open slow over network

We have about 4 pc's with XP SP2 and a windows 2000 server. Everytime we try to open any word, powerpoint, excel or lotus 1-2-3 files over the network it takes about 30 seconds to open.

This only started happening recently and was working fine before.

We are all using the 2000 edition of word and excel.

PLEASE can somebody help? I've tried looking everywhere for a solution but nothing seems to help

This is happening on all the computers, at the same time, when all were working fine before, so I doubt it's windows xp

Edit:

I just tried installing OpenOffice on my pc, and files open fine with that. But everyone else still uses Office 2000 and don't wanna change because they know Office.

*sigh*

Still doesn't explain why it's running slowly

Files opened locally open fine, also I tried un-installing the anti-virus, disabling the network printer, re-installing drivers for the network printer and still nothing

Only thing left to do now is try safe mode with networking, will do that and let you know.