I *think* I might be having the same problem. I was flying from Newark to LAX at 8x time compression and the aircraft was unable to stay on course.
Also, for some reason, after I disabled auto-cruise after the problem occurred, the aircraft got stuck in a shallow left turn, but the navigation displays were indicating a steep right turn. I tried switching autopilot heading select mode on but it just kept on turning. As a last ditch effort, I disengaged the autopilot and autothrottle in an attempt to regain control, but the aircraft was completely unresponsive. It did, however, appear to hold a constant bank angle, altitude and speed even with A/P and A/T off.