I, too, am having similar trouble. I have a desktop with a Belkin
wireless router. After about 10 minutes online, whether email or
surfing, I loose my connection. Once this happens my laptop
(wireless) and my other desktop (wired) continue to work OK in
Windows. I have to reboot my PC and I'm good for another 10 minutes.
I did not have the problem before a clean install of Ubuntu 7.1, 64
bit. I like Ubuntu too well to quit, but I don't know enough about
where to look for a flow chart of diagnostics to find and identify
the problem.