I am having the same problem. Do not tell me to recreate the volume, that is not an acceptable answer. It is disappointing that SanDisk has yet to give a solution to this. I see posts from like a year ago and they all end with some user posting this link:
I have remoted U3 from my sandisk years ago and have no intention of putting it back on. I AM NOT USING U3 and the drive is not recognized on windows 7 unless the system is booted with the drive plugged in.