Depending on the location of the desktop, I ran into a similar problem at work setting up a hotspot. Turned out that the desktop was actually on the floor under the desk rather than on the desktop, and the baseboard of the walls had metal mesh and supports in em (newer building, office inside a grocery store). I switched to a USB device rather than the internal PCI card, and placed it on a shelf about 4-5 FT up on the wall. Same sort of thing happened at a motel office, (older 3 story with cement load bearing walls with metal rods in the concrete). Same thing, PCI card dropped connects, switched to a USB device and placed it elsewhere, no further problem.
Also check the linksys website, they have some firmware updates (and installers for them) that make it much more stable, a must if you are thinking of going to SP2.