USB Flash Drive Integrity Checker

Hi,

I am a heavy user of USB flash drives. I recently had a minor issue
with a couple of files I copied to a hard drive. They were not exactly the
same as they were on the flash drive. A file compare exposed a change.
I copied them again from the flash drive and the second time they matched.

This is the first time this happened. This particular 2G flash drive I
use the most. After I copy all files from it, I plan to "Format" it.

Does anyone know of an integrity checker for USB flash drives?

Thank You in advance, John