Are you trying to use the USB dongle software to control the WiFi connection? If you are then that may be your problem. It's generally accepted XP's built in WiFi Manager is better - and if you try to run both you will get problems.
Having said that I have a Netgear USB WiFi dongle that produces the 'blue screen of death' on one laptop but not on others, even when run using the XP WiFi Manager.
I personally prefer mini-pci cards or PCMCIA cards over USB dongles as they seem more reliable.