Steam Help

[Multiply]

Hey Guys,
Quick question here. When I open up Steam and want to play on CoD4 Online, this pops up:

Error: Keycode in use. Please try again later.

I have been playing on it fine all day, but this has just started happening. How can I fix?

 

[Method_mybb_import12907]

Ehh did you buy CoD4 yourself or did someone give you the code to get it?