So...i fixed the problem myself!
I dont know why Bis cannot say something!
How i solved my problem:
I have 896MB graphic memory, but it always adressed it new to 1792MB!
I had to write the ArmA2.cfg myself and set in on "write protection", so ArmA2 dont rewrite it again!
Then Securom made a lot of trouble...so i have to use a ArmA2 nocd exe...now i have no troubles at all anymore!
Maybe it works for other the same good!
Sorry for my bad english!