This is quite normal. To stabilize the setup I either move the wireless router closer to the laptop or set the connection to a 1 megabit speed so it doesn't try to go too fast.
Moving the base unit might be as simple as moving it to the floor (it could be on top of a desk) or trying different corners of the room its in.
I recently installed a belkin wireless router on the second floor of my house and a belkin wireless notebook card on my laptop which is in the basement two floors down. My signal strengh is pretty erradic. It goes from 99% and superfast to 34% and kind of slow to no connectivity at all. Is there anything you can do to improve the signal without moving the computer? Or is this just a nuisance that you learn to deal with? Thanks