Originally Posted by Charles Kenyon

This is a known behavior with documents stored directly to mobile media, i.e. a "stick," from within Word. Doing this produces corrupted files. This has been the case with every version of Word from at least Word 97.

Never access (Open or Print) documents on mobile media from within Word. Never save or edit documents on mobile media from within Word. Instead work within Word only on documents saved to your hard drive. Then copy documents to/from mobile media from Windows.