Mercenaries 2 fps problem

hello
having recently acquired merenaries 2, I wanted to try but at the setup menu I was having problem with: 1680 * 1050 resolution cause it was not there. I am therefore closed on 1280 * 720 (HD ready) with retail background (HD 4850 ^ ^). So when I started the game, I was surprised to see only 7 FPS in average, I wonder what can the problem be, my graphics card is upto date (catalyst 8.10), I have no problem with other games (pure bottom has turned a 60 fps). Please help me, thank you in advance .

I think this game is poorly optimized. I also saw it running on 20 FPS on a level so thats not awesome graphics in the game itself it seems.

If I were you I wouldn't have bought this game. I liked the playable demo, everything was ok with gppd level graphics and even in resolution 1680 * 1050 ok ...
But when I played the complete game, I also had this resolution problem with 1280 * 720 and there are also some graphics bugs that I noticed with background in white color. So this game has got lots of problem in itself only.