Ok, I know this game is pretty old..and I'm one of the few that still play it..I play on east server Hardcore ladder.
East server has this problem as of late..and no one from Blizzard/Activision will aknowlege it or care about it etc..

Go to create a game..or join a game..and you constantly fail to join the game..
Screen goes from load screen to black and text : Fail To Join Game
sends you back to game channel / lobby..cannot create or join games for hours on end..very annoying and unnerving..

Pretty sure this is only occuring on East server.
Tried to make this as straight forward as possible as many may not remember the game or know it (nice rock you live under there).
And The Games' tech support is of absolutely ZERO help at this point...