I have the same for my laptop (WPC11 v4). I have to put a finger on the card to get cable speeds. I contactedlinksys today and tey should be emailing me withing a day or 2. Try holding the card on your laptop and see if that works. BTW I prefer just running a cable from the router to the desktop. 
Also try changing to channel 1 or 11 since they are not overlapped by other 2.4ghz device frequencies.