Xerox Documate 272 scanner with latest driver (directly connected via USB 2 cable)
Open Acrobat, Create PDF from Scanner, choose Greyscale (it really doesn't matter, but this is the one we use 99% of the time), and wait for the scan. It may work perfectly fine for 4 out of 5 times, but then on the 5th time the scan does not start up and you get a "An unrecoverable error has occurred. Operation Stopped." error window.
If I go ahead and try to scan again, I will get the same error. If I quit Acrobat X Pro and then open it back up and go through the scan process again, it might work perfectly 4-5 more times, and then BOOM the same "an unrecoverable error...".