Got a(nother) error in Vietnam: The Experience, Can not shoot D: Options

[Aardman55]

I just recently played the game when i couldnt shoot.
In the normal game it works great, but when i play vietnam: The Experience it just manages to empty 1 magazine, and the rest wont work.
I press left mouse, but it doesnt shoot.
The right mouse works and when i want to minimize the left mouse button works too.
And sometimes, after time, i can shoot like 3 bullets and then it "refuses" to shoot again.
I restarted many times and it is only the first mag which works.
Please help.

PS. I use the latest beta version (beta since the normal oa crashes for me in the first 10 minutes).