[Gameplay(?)] Function Key Stuck

I'll be in the middle of a game (actual position of game varies) and it will happen that my "function key" will kick on when I am NOT holding down ALT. Every right-click merely pings, no keyboard commands work, and I can't even press enter and type to tell my teammates what is going on. The only way I can even hope to fix it is to ALT+Tab (the only thing I can actually do) and go back into the game. And that hardly ever works!