I have an error joining a game (random game) with a friend. If I join a game and I get there first, if my friend follows, he gets the "your connection is lost" error and gets kicked off of battle.net for a time period. If he joins a game and I follow him, I get kicked off as well and get the same message. After we wait for like 10 minutes, we could go back on battle.net. This hasn't never happen to me until now. Months ago, I could follow my friends and they could follow me with no problems.
Other information: This is my first time playing with this one friend. If you guys need more information, please do ask.
Are you and your friend sharing anything at all like the internet connection or game cd-keys? A 10 minute restriction like that is usually given for spamming. Do either of you use any mods that might be outputting a lot of text upon joining? Does it happen only on custom games or does it happen when using Blizzard maps too?