I logged in and selected multiplayer and I was asked to enter the serial number and so I entered the CD key and it was verified and accepted but when i tried to join a server it states that the serial key that i have entered is wrong. How is that possible unless the cd key is different from that of the serial number. Can anybody answer my query thanks in advance.

Yea same here ,what gives?

The MP servers for PC are still down, not sure when they are going up but it should work then

Can an admin confirm that the servers are currently down?, so we can all calm down and stop losing it over this issue...

Okay, when your logged in, before you try to join a game, at the top right, it says "NEWS: Servers are currently unavailable." So that is likely the problem... once there available hopefully we dont get this error message.