I was playing in an AS match and received a game invite. First, my status should have shown BUSY and I should NEVER get an invite mid match... but more than that, when I went to decline the invite, it closed my game window with the standard "an error has occurred" message forcing me to reopen the window and continue the game.
As I was doing this the INVITE appeared AGAIN! I ignored the tab and instead tried to change my status from the main window to BUSY. This time the game window not only closed, but I was completely logged out of WGT.
I closed all my browser windows at this point, reopened, logged in and rejoined the game... but not before manually changing my status to BUSY. I was only glad I did not have another problem as it would have been my third disconnect and would have resulted in an automatic forfeit on a AS match we were 2-Up with 3 to play.
I have never experienced this issue before (receiving an invite during a game). I assume this is a bug as I should never receive an invite during a game -- at least it has never happened before.