Adobe Photoshop CS5 Could not initialize Photoshop because of a program error [FIX]

Launching Photoshop CS5 on Windows XP gives the following  error message after loading splash screen.

Adobe Photoshop CS5 Could not initialize Photoshop because of a program error

There are no error codes shown and no errors in windows system or application log.
FIX : To fix hold down CTRL+SHIFT+ALT when you click to launch CS5. This clears preferences and then it all loaded ok.