I was having problems with losing interent activity and it being very sporadic at best. I would have it for 3 or 4 hours and then lose it for a day. It was very annoying. Sometimes if I walked upstairs and reset the modem and unplugged router then I could get the connection back, sometimes I couldn't.
The cable guy said it must be a problem with my router. So I called the Linksys guys. I have a Linksys WRT54G. They took me through some steps that basically reset my router. It appeard to solve the problem as I was able to connect via wireless. However, since then my interenet has been extremely slow to the point where I can't even browse the internet b/c it times out before it can load the page. It has to be a router problem b/c while I plugged straight into the modem it works fine and is very fast.
Another problem that I have is with my laptop, that I use at work as well everytime I bring it home in the evenings it will connect to the wireless, but with "limited or no connectivity" even though the signal is strong and I will have to Start ->Run and type in services.msc and Start the Wireless Zero Configuration. After that I can connect via wireless, but again it is so slow that it is no even usable.
I went out this morning and bought a new router thinking that mine was just bad, but I am having the same issues with very slow internet.