Another Password Incorrect! (cd:260) question.

[EvilMcBad]

Hi

I already have a steam account and profile for playing MOWAS, all works well & I can play online.

My brother has been watching me murdering my 3d opponent and wanted to join in, no problem, so I buy him a copy of the game.
I enter the CD key and register the game without a hitch. Then he tries to go online and it says 'Password Incorrect (cd:260)'
I've reset the password 3 times but still get this message.

I contacted support yesterday, but it's the weekend and probably won't hear back till next week.

I guess the big question is ..........
Have I made a mistake by adding his account to Steam on my PC?
(My game and account is also on this PC)

Thanks in advance.