Steam lost controls after alt+tab out of game.

[PbLead]

Playing with an xbox controller I lose the B key and subsequently the escape key on the keyboard when I alt+tab to look something up. I have to superquit and restart the game to regain these functions. Clicking on the (esc) Icon allows me to complete the function to get out, but I lose those keys. 

[PbLead]

To clarify, I lose the B button on the xbox controller, not the B key on the keyboard.