Product Installation Unsuccessful Please Reinstall Error 24

HELP! I have had Corel X4 installed for about 3 months then all of a sudden it has stopped working.

Everytime I try to start the app it comes up with "Product Installation Unsuccessful Please Reinstall Error 24" and closes. We have this installed on quite a number of computers with different legit keys on each.

I have tried repairing the installation through add/Remove programs with no success, one one computer tried uninstalling then reinstalling but when installing it comes up with "Invalid Key" when trying to reinstall, which is weird because it worked before and is legit. All computers running Windows XP and had CorelX4 SP1 installed. Have tried installing the Hotfix1 (no sucess).

Have looked through the forums here and can't really see anything that will help. Would really appreciate some info, cheers.