Weird bug - main gun fires once then hardly at all

[SausMasterjimminysausage]

My hard drive with all my games died, and I transferred everything to a new HD. While I was at it I bought a new mouse. Now when I go back to playing Sturm, everything is okay, except when I fire my tank gun with mouse 1 it fires fine the first time, then hardly ever after that. It sometimes fires when I press down both buttons. MGs are also unreliable when secondary, and don't fire at all when primary. I tried mapping also to the joystick but no love. I tried using my old mouse again but the exact same thing happened. Any idea why the button might be working once, every mission start, and then never again?