This USB adapter was causing problems on my nearly fresh installed Windows XP SP2 Professional system. I am using the "Fritz Box WLAN7050" as Access Point.
After I had installed the latest drivers (Version 5.0.2102) the adapter disconnects itself after a short time (5-25 minutes). I was using the Netgear configuration utility to setup my WLAN connection.
After digging the internet for similar problems (I found a few hits) I decided to go back to my previous driver (originally supplied with the adapter) and deactivated the netgear WLAN configuration utility. I now use the Windows WLAN network configuration and it works perfectly.