"The only thing that fixed it was rolling the update back"
I also got the squuiizzzing loud noise, when stream starts through the optical on my Ultra on the 8.01 firmware...
But how do i roll it back to previous version ?
Press Home 5 times, Fast Forward 3 times, and Rewind 2 times. Should take you to a secret menu with an option to "Update Firmware". This should actually roll your firmware back to the previous version.
Please make sure to log a ticket about the issue with Roku - the more reports they have the more likely we are to see a fix in the next update.