Ok, I managed to solve my lag and crashes. The solution was to edit out flares and starshell gun. Don't know why this is so demanding on my (quite good) HD6990.
I really hope TDW will find a solution to implement flares without lag (I'm not the only one experiencing lag with flares). If someone want help with editing out flares and starshell gun just PM me and i will gladly help you.
I have still the problem with my mouse cursor unattaching from the view mode. This is very irritating, specially when i track a ship with my periscope and suddenly my cursor pops out and I need to right-click again to turn the periscope or when I'm in hurry and the cursor just pops out all the time when I'm trying to run down from the conning tower for emergency dive. I have narrowed the problem to part3 of MMM. I hope someone can help me solve this because I'm so near a pleasant gaming experience now...
