'Can not connect to online service'

Hi!

I have had this issue since the start of 2009 (approx) and I am so sick of it.

Whenever I start up Call of Duty: World at War (PC Version) it says 'Can not Connect to Online Service' and I can't play online at all. 1/5 days it does work though but I am tired of having to play singleplayer because the online doesn't work...

Does anyone have any solutions? My internet connection is fine. I have tried turning off my firewall, I have restarted my computer loads of times and still it doesn't work.

I really hope this doesn't happen when I get Modern Warfare 2...

Thanks in advance.