networking issues

hello! about a month or so ago i asked all of you wonderful people for help on buying a router. i bought the linksys WRT54G and it's been working well - at least on my laptop. however, after a week or so, the internet was running incredibly slow on my desktop. the desktop is connected directly to the router, the laptop i connect wirelessly.

I called Comcast and told them about the problem. The tech reset the modem/broadband and that seemed to help. But after a few days it slowed down again. He said that we might see a small difference in speed with two computers connected, but it shouldn't be that bad.

i read through some of the posts below where people had similar problems, but i wasn't sure if any of those solutions would help.

EDIT: when i disconnected the desktop cable from the router and plugged it in directly to the modem, it worked fine and was up to speed.