Not Playing Original Game - Game Unavailable on Steam - What the ? Help needed

I know this has happened with so many people in the past but this has just happened to me now.

I was playing a league game when all of a sudden FM12 shut itself down and came up on the http://www.footballmanager.com/support/game_problem_en_us.html website

Football Manager has detected that you may not be playing an original version of Football Manager 2012 and the game has therefore shut down.

If you believe you are playing an original version of the game then please contact SEGA support.

If you are playing a non-original version, you'll not be able to re-load the game. Please click here to purchase a legitimate version of the game, which will support the making of future versions and will also avoid seeing this message again.

then a Steam box popped up saying

Steam - Error

This game is currently unavailable. Please try again at another time.

What on earth do I do to get this game going again ?

I orignally pre-rdered it from Steam.

thankyou

what anti-virus do you have? I had this error yesterday randomly, turned out it was my Bitdefender Antivirus 2012, uninstalled it and its running fine now. Now using Trend Micro Titanium 2012 and no problems with FM 2012.

There are a couple of suggestions in the FAQ thread about these error messages so start by reading that.

Update - I just rebooted my computer and all is ok. So far. thankyou for the help so far. I use Microsoft Security Essentials for my Anti-Virus. Never had a problem with FM10, 11 nor 12 up until just before.

Just hope it doesn't happen again.