nvidia driver issue?

[LeadCommando65]

Hi,

I bought arma2 last week. I was very impressed by the good performance on my pc (~25 fps woods, up to 40 fps open range).
2 days ago I updated the drivers for my nvidia graphics card due to another problem I had with some programs. Now I have v185.85, last one was v178.xx. Playing arma2 after that gave me really bad slow downs (~10-15 fps), when looking at many bushes/trees which overlap. It's unplayble in those sceneries .
I don't think it's my pc:
Core2Duo E8400
Asus P5Q-E
4GB DDR2 800
GeForce 8800GT
Windows Vista x64

So, I think it's just the driver. Can anyone confirm this lacks? All I read about were heavy issues with ATI cards, no word about nvidia.