Bridge 15.1.1.729 hangs when previewing any mp4 file with GPU rendering

This was working fine in hardware preview on Aug 12. Now on Aug 14, any attempt to preview a .mp4 file hangs the whole Bridge client requiring termination and restart. Other file previews are fine.

No other system updates have been performed unless Adobe silently updated MediaCore etc in the last two days. 

Post-problem, updating to the latest Nvidia driver 580.97 did not fix. Only software rendering works as a workaround.