Register CD Key problem

[Keptron]

Yesterday I had register the CD Key, today when I went to play 2 minutes ago it was unregistered and it wasn't accepting my CD Key, what happened?

Error: Serial number error 47 (1) has ocurred.

Edit:
Ok, this will look strange, but I restarted the computer and the game was registered and playing normally again.

[JohnBart]

Welcome to the club, me and my buddies has the unfortunate state that our CD-keys always unregister after 2-3 rounds played on non-demo maps...

[Blackopunit2]

My demo registers randomly. I can play non demo maps in the demo, then it un registers, re registers. Sorta random. People who just got the demo have theirs registered cause i had a demo server on centro and a guy joined and i asked if he bought it he said no, and his was registered. Is this a known problem?

[JohnBart]

It is a known issue of the Steam version.