Also, what version are you using?
That issue seems to be possibly related to a issue with 1.7 and its copy protection...:evil: ..If the executable has been tampered with, using a loader (not fully reversed), that error message WILL pop up, rendering the hacked beta 100% unusable. Its extremely rare that it occurs on legit 1.7 builds that you donated for.....and not given to anyone else.
Other than that, with 1.6, the error shouldnt occur at all.
Again, system specifications will be nice.