I had a similar issue with my HP laptop. It would constantly drop, especially if in a data heavy download or stream. I found that installing an OLDER driver for the built in wifi eliminated the problem.
Similar issues appeared after I upgraded to Windows 7. Then I somehow discovered security settings in the router (Dlink D-615) could cause issues. Setting the WPA mode to "WPA Only" in the router configuration seems to have taken care of it. So yes, cards and routers don't always play nice together.
Of course my Nexus One phone does not care for this router too much and drops the connection quite often. I'm thinking of switching to a Linksys WRT54GL running DD-WRT firmware since that seems rock solid on anything I have tried to connect with on another network I maintain.