on my laptop, it was my firewall. When i would check the exceptions, it showed that CoH was on the approval list, but it still failed to access the interwebz. What i wasn't seeing was the little pop-up that would come up behind CoH that would cuase it to flicker a little bit when i was trying to log on, and went away when i got angry and closed the whole mess. After every update, patch or anything it was asking telling me that the program had changed, and asking me if i still wanted to allow it access to the interwebz.
Either alt+tab when you try to log on to see if you have one of those notices, or just add it to the exception list again, and see if that works.
( if you turned off your firewall or already did this, i just wasted 3 minutes of your life, sorry )
... sometimes anti-virus software'll do it to, becuase tthe updater changed and the allow button wasn't clicked ( mcAfee was killing my CoH on my desktop for awhile ) you could check it...