How Can I Make that Damn Burning Oil Wheel Work?

In the Vergen Beseiged quest, when Geralt and Zoltan split-up to open the gates that dump burning oil upon the enemy I cannot get the wheel to turn at all. Geralt grabs onto the wheel, but no matter how much or fast I jab the left-mouse button the progress bar doesn't move. I suspect that my PC is having trouble with all of the action as Geralt fights in slow motion on his way to the wheel. Do I need to adjust some type of game setting? Thanks for any help!