Help: Volume knob doing something funny

To start with I own a Big Al 5 SSS. The problem I am talking about is that when I turn my volume knob all the way up it cuts completely out, but if I just turn it down a fraction the sound comes back full force. Could this be a volume pot issue? Or could be a preamp issue? I only own one bass right now and gig weekly so I am hoping someone here can give me some help. I will contact customer service if no one here has advice. Thanks in advance for any help.