I'll answer in order you asked:
-yes I had a Windows Update, but I think the problem started before that.
-I have an anti-virus running, but it was always there with no problems before.
-Yes, the compiled game is slow too. It's not the game itself, but the settings window. Once it appears, everything else is OK.
-there's no difference if I enable/disable 3D acceleration.
-No I didn't, I might try.
-WME version - 1.52, Windows version - XP Home edition SP2, video card - ATI MOBILITY RADEON X600 SE
-other games run ok. I'll have a look at dxdiag as well.
To odnorf: No other 3d application running.
My point is, that it worked perfectly, on the same configuration, but the day before yesterday Istarted to have this problem, although I don't remember changing anything in OS nor system.
Thank you, for your reply.