Valve has restored access to Modern Warfare 2 for "over 12,000" Steam accounts, after the PC players were mistakenly banned from playing the game by the developer's anti-cheating software.
IGN reports that Valve boss Gabe Newell sent an email to all the affected users to apologise and explain, and that Valve given them all copies of Left 4 Dead 2 for free, with extras to pass on to a friend.
The problem, which occurred over the past two weeks, saw Steam's anti-cheating software banning legitimate players at random.
"The problem was that Steam would fail a signature check between the disk version of a DLL and a latent memory version," said Newell, according to IGN. "This was caused by a combination of conditions occurring while Steam was updating the disk image of a game."