A multitude of users are reporting that they are unable to play Bioshock on their PC today due to what is likely a patch by either 2k or AVG or perhaps a combination of the two.

When users try to launch the Bioshock Main Executable to play, if AVG Antivirus is installed, it hits on Bioshock as a virus and will not allow it to launch. Even if users tell AVG to ignore the file, it will not launch. Healing or quarantining the file leads to equally messy results. Healing the game's .exe file renders it unplayable, though the virus warnings will stop.

>> BioShock Latest Patch Work-around