Does anybody else gets a virus warning on flatout.exe?

No, what av are you using?

I'm using Comodo Antivirus.

I use COMODO as well. Tis a false positive. You'll get it on Need For Speed Underground 1's "speed.exe", Colin McRae Rally 3's .exe and, FlatOut.

Open COMODO and click "View Quarantine", once in there locate the FlatOut exe file. Right click it and choose Restore. It will make an exclusion and restore the game's exe file for you.