I've had many problems with usb flash drives and laptops. An ongoing one is usb 2 drives defaulting to usb 1 speed. I put that down to power, and assume that a powered usb hub might cure it.
But a more recent issue is a 16G Kingston usb 2 drive appearing to an Acer C2D laptop (TM6592) running XP as full even after being formatted. The same drive is working in a Thinkpad T41 running Win7. Tried shutting the laptop off and restarting to clear any hangups, but the result is the same. It's not the flash drive; two identical ones behave the same way. So it could be either an XP issue or the laptop. The XP will be changed, I just don't have time right now. A similar Kingston 32G flash drive worked properly in the Acer.