USB flash card not read by XP Pro.

Just bought USB Flash mem (128mb/2.0), 2k & XP compatible.
It works fine without any problem on 2k's.
When connected to XP's, sometimes it will work just fine but sometimes, it never even opens up.
Symptoms - PC recognizes the device, already self installed the driver, and even has "safely remove" button on the bottom. However, can not open the device's actual content.
This happened to one other XP, but fixed the problem by changing the drive letter from drive manager console from system manager. The PC in question, won't even let me open the drive manager when Flash is connected.

Any Suggestions?