I had the same issue occur for me. I have not completely isolated the offending program or service, but I have fixed the problem for my system running vista 64 bit.
There was a conflict from service that was running in the background so I went in to msconfig and did a custom startup in which I disabled all services except those from microsoft from loading. With this clean boot the problem disappeared immediately. I have been slowly adding back services one at a time to the selective startup menu until I find the offending one. It has been a while since I did this in XP, but I seem to recall that the msconfig utility is present in XP as well, so it should work for you in that OS as well.
Proceedure I followed is the following:
open msconfig
On the General tab, click selective startup.
Under selective startup click to clear the Load Startup Items check box
Click the Services tab, click to select the Hide All Microsoft Services check box, and then click Disable All
Click OK
When prompted click restart
After the computer restarts, open the program and see whether the problem is fixed
To return the computer to a normal startup mode
open msconfig
clidk the General tab
Click Normal Startup - load all device drivers and services, and then click OK
Wehn prompted, restart the computer