Like many my USB flash drive stopped working with Windows 98% of the time. I used Task Manager to manually kill all the Samsung Kies processes (two) and it’s worked fine since.
Samsung Kies is a different process from the USB. Drivers are usually handled by the OS. I would suggest to have a WIndows update and hope that there would be a driver update for the Sandisk USB too. 
@joelmch wrote:
Samsung Kies is a different process from the USB.
But is known to cause compatibility problems with SanDisk flash drives.
