Not that you have to be very careful in copying Access files to flash/thumb drives! There are many, many reports of this causing problems, and the best guess, as to the cause, is that people are doing this in too big of a hurry! Apparently many of these drives report that the copying process is complete somewhat prematurely, when dealing with Access files, causing part of the file to be 'left behind,' so to speak! The reason I consider this as the probable answer is that many people report the problem resolving when they give the drive an extra thirty seconds or so, after it reports the copy completed, before removing the flash media.
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007