I don't know, if this has been mentioned somewhere else before, but I've encountered a problem, when you have primed a grenade, but instead of hitting the "prime"-button again, hitting another grenade button, like impact grenade.
When you do this, you aren't able to shoot any longer, until you pick up another grenade (which explodes right after you picked it up).
I'm not sure, if this is just my stupidity, but maybe you should change this.