USB memory sticks failing selectively

I purchased some time ago a PlexTor PX-F256 memory stick. It has been working fine, but all of a sudden it stopped working on XP but continues to provide top service on PC’s running W2K. I have tried many different hardware but with no result: the ones with XP (SP1 & 2) don’t digest it, the ones with W2K run fine. I’ve tried also on equivalent if not same hardware to exclude particular brands from the hunt. Only in rare occasions I am able to use it on XP as well. Does anyone have similar experiences? Or a solution.