Run the configuration program and switch to 640x480 until getting past the cutscene at the end of act 1 (pick up anything you want to bring with you first, as this is a one way trip). If you complete act 2 before the next patch comes out, you may have to repeat this workaround.
In general, real time ant-virus should be disabled when playing games. You computer may be able the performance drop they cause, but they can also cause conflicts.
