So you can get to the Linksys access point configuration page (192.168.1.1 or whatever) from the laptop, but not access the internet from there? If so that would rule out WEP or wireless issues (I would guess).

If you can't get to the setup page I would try again, disabling WEP to see if that does anything.

I went through a phase 4-6 months ago where I'd lose the network about every week to ten days. Not sure how I solved it - it may have been a firmware or driver update.