Hi,
yesterday I found a new driver on this Website (Version 3345).
I installed the driver at the same way (deinstall until Mirosoft basic Driver, Install with Device Manger).
After Reboot, Sound works.
Turning off/on the TV, Sound is lost.
But, if I reboot the PC, sound works, and now I change the input on my TV to my Bluerayplayer and switch back, Sound survived. Sound is only lost, when the TV is turning off.
Its not the solution, but its an beginning :-)
Greetings from Germany
Andreas