Wireless Connection Slows Down on own

I'm running WinXP home SP2 with latest patches. My computer connects through a wireless Linksys 802.11B router. I'm using a D-Link DWL-520+ wireless PCI card. The signal strength of the WAP is very strong.

I've noticed that my wireless connection speed starts out (after boot) at 11Mbps but drops to as low as 1Mpbs once data starts flowing. The 11Mbps speed is restored after I repair the connection, but often goes back down to 1-5Mbps.

I've tried the connection using only Wireless Zero Configuration, and I've tried it using WZC and the DLink utility (Whose features I can't access when WZC is running incidentally) with the same results. I used to be able to connect to the WAP without using WZC, but I seem to have lost that ability with the upgrade to SP2.

Ethernet connections have no such problems.

Any suggestions would be greatly appreciated.

Cj