SOHO stopped comunicating

First off, I'm not a networking guru.
I have a DSL 2Wire modem with a linksys WRT54GS wireless router connected to it for my notebook to connect to the internet and my network. (Desktop is cabled to the 2Wire) Recently my desktop and the laptop have stopped talking to each other. You know, husband and wife style. They can see each other but they won't talk to each other. I can access the internet with either machine. If I try to connect to a shared folder I get the error message: "notebook (or desktop) not accessible you may not have permission etc,etc. Not enough server storage available to process this command." My home network has been working flawlessly for several years. It has only been in the last few days that I started to see this problem. I went thru tech support with the 2 wire modem (thinking the problem was there) but no. According to them the modem is fine. My problem is on my end. I have searched and searched the network settings but can find nothing. Like a blind man trying to find his way out of a maze. I can't see the exit.
Would appreciate any help anybody can give.
Both machines are running WinXP