Then that's the problem and why they don't work you must let the backup manager do the work for you.
1.) put ps3 game in drive
2.) launch multiman
3.) hit the corresponding button to backup the game directly to hdd or to external
4.) wait for multiMan to make a backup (might take a while depending on how big the backup is)
5.) after it completes then hold Select on the controller and Push in Left analog which is L3 to refresh the list
6). Pick the game from the list with X then it kicks you back to XMB
7.) Hit X on the controller on the Disc Icon which should be the backup and it should launch just fine if not then you might have a backup that needs to be on an external hdd to run correctly and if so just Hit R1 until you get to the File Manager and Move the entire folder from Left to right to the external hdd and put it inside a FAT32 external which has either a GAMES folder or a GAMEZ folder in it once you get the game there you hit R1 until you get to the list of backups then repeat the Hold Select then hit L3 to refresh the list then highlight the backup then Hold Select then while holding Select hit the X button then it ask you if you want to emulate it say yes then it kicks you back to XMB then pick the Disc icon like normal then hit X on it and it should work just fine.
Wow i just typed out a whole damn step by step
Hope this helps you get your backups working let us know how you made out