Some players of "Alien vs Predator 3" on Steam have reported issues related to the Steam API.dll. These issues might manifest as:
If you own the game on Steam, right-click the title in your library, go to Properties > Installed Files , and select Verify integrity of game files
While not recommended due to potential risks, some players have reported success with replacing the Steam API.dll file with a version from an older or newer Steam client. However, this should be approached with caution and only done if you fully understand the risks.