A damaged "audio" cable/connector. can cause that
Do you mean on the mobo, or outside the case? When I gently try to wiggle the speaker cable coming from the back of the motherboard nothing happens. Also the buzzing/freezing happens at fairly regular intervals when it happens. For example freeze, 2 seconds, freeze, 2 seconds, etc. The freezing and the time in between freezing are variable at any given "problem time"
Thank you for your help so far, by the way.