Producer X3 - dll Files disappearing

going back to an old drive, and when I re-open X3 after a re-boot, several DLL files get erased, turned to size 0k. I can replace them to re-open X3, but that is no solution. These are the ones:
 
TTSlibsndfile.DLL
CJLibrary.DLL
 
Any idea why this is? Guess will have to re-download the whole X3, but I'd like to know if there is someone else wrong with my drive, in terms of a virus or something. Scans show nothing.
 
Thanks.