jliubit of a dead thread, but I've recently run into this issue too, and I'd like clarify for more future Googlers that basically the Windows Play/Pause key command causes a "g" input in TF2. Anything you have bound to g will be triggered by that button.
whenever i press the play pause button my keyboard starts registering my inputs like 10 seconds later for 5 minutes, and its never done the g input thing, any thoughts?