That is odd indeed. I assume you tried a complete PC restart (in case of one those unexplainable glitches) ?
I would try and bind it to another key first, like "9" and then try to assign "B" to something else to see if the problem happens there too. If the 9 key works and the B key still brings you to the menu, regardless of where you try to assign it, my guess is the problem is the keyboard or the keyboards software. i.e. somewhere within the keyboards software the "B" key has an assigned macro of some sort. Hope this helps!
V/R Fawlkon
Game On!
Please don't forget to select "Problem Solved" and/or XP button if this helps or fixes the issue!
