Valve has unbanned over 12,000 Steam accounts from accessing Modern Warfare 2 for the PC after gamers were mistakenly banned from playing thanks to their over-zealous anti-cheating software. The software was randomly banning normal gamers seemingly at random.

Valve head-honcho Gabe Newell has sent an email to all the affected users. He apologised and explained the situation to everyone and gave them all copies of Left 4 Dead 2 for free. What’s more, folks will have additional copies to hand out to a friend.

“The problem was that Steam would fail a signature check between the disk version of a DLL and a latent memory version,” said Newell. “This was caused by a combination of conditions occurring while Steam was updating the disk image of a game.”