If you are having trouble joining a friend's game or other servers, or just as good maintenance, you need to update your game.
The Major updates appear to be automatic, but many others do not update just by starting the game.
Find your battlefield directory and the the BFBC2UPDATER.exe run that and you can see how far behind your version is or isn't and update of course.
I can now join friends on servers again. 
Current version (which you can see on the lower right of the startup screen, or when you run the updater, is something like 589035.
