Digital/Physical keyboard not sending input on occasion
You can try this:

Go into Settings>Application Manager and locate your keyboard.  This could be listed a few different ways, depending on your phone.  For example, I'm using Swift Key so that's what mine is listed under.  It could say software keyboard, or whatever for your hardware keyboard.  Anyway, once you find it, tap the button to clear the cache.  Unless you have a bunch of custom settings you are probably safe to clear data as well.  Once that is done give it another try.  This will solve a lot of annoying keyboard issues, but as you said, who knows.  It could be something else going on where a reset is your best bet.  Hope this helps!