Network woes

I have an 8-machine network mixed with Win98, Win2K and XP. All was fine until one Win2K machine started refusing access to the XP machine. Nothing has changed, and the 2K machine can still access the XP machine just fine, but not the other way around. They ping each other just fine, and I've switched router ports and cables. I also tried resetting the shares nd permissions on the 2K machine, giving everyone full access and the XP user Admin rights. Still, a one-way network! This happened overnight. Any sugestions?

-- Ah sh*t! sys64738 --

Here's a screenshot of the error box:

http://www.camerasupport.com/temp/errorbox.jpg

It worked fine the other night, then went bad all on its own. No permissions were changed, and setting new ones has made no difference. ARGH!

-- Ah sh*t! sys64738 --<P ID="edit"><FONT SIZE=-1><EM>Edited by mavicator on 11/19/02 10:27 AM.</EM></FONT></P>