Make sure the router is set to "mixed" on the wireless side and you won't have to worry about which Wifi card someone has.
Your saying that your getting internet dropouts on both the wired and wireless side doesn't make sense unless the router is bad. It's possible you got into a bad batch of them...but you're right, these things are made by the thousands and are usually stable. I have replaced cheap Linksys routers though, every couple of years.
If it was just the wireless side, I'd ask you how many wireless networks your system sees when it does discovery. If there are several around, try using a different channel than the default 6 for your wireless broadcast. This can be done from the Linksys Router Console thru your browser. 6 is the default, try using one of the non-overlapping channels as far away from 6 as possible. You'll get no interference, as long as your neighbors aren't using the same channel you choose. Since most people don't know about this, it isn't likely.
zeroth