try upgrading your wireless adapters drivers. my girlfriend has a dell and it got shitty range or wouldn't connect at all. I downloaded and installed the newest drivers for her wireless card and so far, no problems.
hmm i havent tried updating my wireless network card, i never have full bars on my wireless connectivity. but ill try that when i get home from work and see how it runs
I have a wireless router for my ibook and PSP, sometimes it does have error joining (all from my ibook, rarely though), once its connected, full bar aways