With Windows, any time the keycode either does not take or vanishes after a period of time, one of two things is happening:
1. The user had security (antivirus, spyware, etc) programs active during installation. This results in a corrupted registry entry that will not "hold" the keycode properly. The solution is to reinstall with the SachsRemove utility as outlined here on our FAQ
http://www.serenescreen.com/support/...bmit#faq10_684
2. Some program is altering the registry. Odds are MA is not the only program effected, just the most noticeable. Other symptoms can include option and preference settings that return to default on their own. This can be caused by legitimate programs and spyware alike. Anything that goes into the registry and alters more than its own keys. Feldon lists two good examples above.
Along similar lines, there was a spyware removal program called Adware Filter by PCSafe, that had us pegged for spyware and would remove the entire program. That's been worked out though and their latest version leaves MA alone.