I just had this problem. Exactly like yours. My answer was to close DVDFab,[B] right click on the icon in the quicklaunch, select “Run as Administrator”[/B] and VOILA!, it’s decoding now.
Since my media center has to run pretty much 100% with the remote, I setup the media center user to have no password so therefore, I restricted a lot of its accesses. But this did it.
If you have to start DVDFab as you stated above in bold you can right click on the DVDFab icon on the desktop and select “Properties” and with the properties open click on the compatibility tab and at the very bottom under “Privilage Level” put a check mark next to “Run this program as an administrator”
Have a nice day