"Hack Detected"

Hi there,
I'm having a 'hack detection' problem here...
In the middle of the game, a window opens and says "Hack tool detected (1)(5.0)" --> or something like that... and the game shuts down immediately. I sweare i know nothing about hacking, i just want to play the game and have fun.

Is there anyone who could help me? Anybody have an idea why can that problem occur ?

Thank you all.