Sudden Inconsistent Wireless Connection

I've tried connecting my computer directly via ethernet and I still have occasional issues with my internet. Previously, I was using a wireless setup and the connection would drop every so often, so I tried changing the router, changing the channel, resetting everything, but nothing helped, and this problem was consistent on multiple computers. So I finally moved my router 3ft from my computer and still had connection issues, so I connected my computer directly to my WRT54g router which made things slightly better, but I would still get an occasional dropped signal or slow connection, and the yellow exclamation would come up. Now I'm connected to the modem directly, and its better, but I still get an occasional slow down or disconnect. What do you guys suggest? As I've simplified the system, the performance has gotten better, but not 100% from what it used to be. Are there things that I can check/do on my computer that may help? Everything (router, modem) seems to be working fine, the lights blink like they always have, until the connection drops of course, but could there still be an internal issue with the router or modem?