The 6031 errors that some Windows users are seeing more with 8.0.1 are caused by other device drivers on the system misbehaving - holding off processing too long. 8.0.1 has better detection of this situation, which can in some cases lead to noise during playback or recording (8.0.1 throws a 6031 error in that situation instead of tolerating it and risking the noise). The down side is that certain systems with drivers that cause this will show 6031 errors more frequently in Pro Tools. The 6031's are less likely at larger playback buffer settings, so you might try that in your Playback Engine setup dialog.
Now if you're seeing this error after downgrading to 8.0, it's possible that you've still got the 8.0.1 device driver installed; this file is found here:
\Windows\System32\drivers\dalwdm.sys
Find that file in the explorer, right click on it, choose Properties, and click the Version tab. If the version is 8.0.1, just delete it and reboot. After rebooting, in the Explorer find Program Files\Digidesign\Drivers and run the DigiDriver utility. This should reinstall the 8.0 driver.
* Now, that said, there is a workaround for the 6031 with 8.0.1, but it leaves you vulnerable to noise caused by other device drivers on your system. If you don't mind that risk, you can try the following, to use the 8.0 dalwdm driver with 8.0.1:
- With 8.0 [cs] installed, make a copy of the Program Files\Digidesign\Drivers folder on your desktop.
- Install 8.0.1, reboot.
- Copy dalwdm.sys from the Drivers folder on your desktop to \Windows\System32\drivers, replacing the one that's in there.
- Reboot.
If your 6031's are caused by this driver issue, this should clear them up. (But bear in mind the risk.)
Edit: If you have any trouble during steps 3 or 4, or if Pro Tools won't launch afterward, run the DigiDriver utility in the Program Files\Digidesign\Drivers to restore the default setup.
I hope that helps.