For the sake of adding my 2 tria, and maybe having it improve something, the same thing happens to me. However my laptop, presario 2500 2.4 xp does it more often. Desktop Hand built 2.8 xp with much more memory and the dreaded radion card does it much less. Lappy connects wireless while desktop is wired, both through the same router. Usually if I am running both lappy crashes first and then desktop, but I have had desktop not crash when lappy did. Maybe it has something to do with losing the ping?
I can fuddle my way through working on my own stuff but am in no way an expert. Maybe this will help though.