Upgrading to 4.0.2.49
I was at 4.0.2.x and moved back to 3.8. Either I don't have the sound issue or my ears are not sensitive enough to tell the difference. I can tell you that for the month and change I was at 3.8 I NEVER ONCE had to reboot my 7100. I was rebooting at least twice a week under 4.0.<whatever>.
I'm just about done with the update to .49 and have high hopes of a loud and fast 7100t