The problem is the game gives you ammo (50/100 maybe) when you purchase the first point in the skill. Since you maxed out the ammo before buying the skill it can't give the ammo that the skill comes with, so it bugs out and doesn't complete the action.
It seems like an easy fix for them, though there's no telling how long it'll take.
Not all of the ammo based skills give free ammo, but I imagine all the ones that do can be bugged by this.
So, keep those drivers up to date...or something
