I have the same issue. I’ve updated both the A4 and Overbridge. I’ve tried various combinations of restarting both machines and resinstalling the updates. I’ve even tried going back to a previous version of Overbridge.
This really harsh constant high-pitched complex sound begins as soon as I enable Overbridge mode on the A4.
It stops if I reboot my laptop but starts again at some point when Windows (7) is loading up, presumably the point where the Overbridge audio driver is loaded in the start-up sequence.
Interestingly, the sound becomes quieter and more like a simple high pitched oscillator hard-panned to one side if I disable one of the outputs on the laptop’s Overbridge configuration screen.
I have all the inputs from the A4 to the laptop disabled and none of the voices have an external input as their osc source, yet somehow it sounds like some feedback loop is created.
I’m hoping the bug is rectified soon as I can’t use Overbridge at all at the moment.