I recently upgraded to 64 bit Windows 8 and I can't Xpadder to function for very long. I got the furthest with Xpadder version 5.3, but after I set up my XBox 360 controller and saved my profile, it basically froze up. I could still access the menus and everything, but couldn't do anything with the controller settings. Version 5.7 did this to me before I could even add a controller.
I do have the compatability settings set to XP service pack 3. Any other guesses?Got it. Run compatibility again. As sophip wrote above. When it runs, select the option that it didn't work. Select that your problem worked better on an older version of windows and then click Vista service pack 2 from the list. Fixed mine perfect.
If it doesn't work try again with one of the other settings listed.