I discovered that Pro Tools kept reporting that its Video Engine was crashing. So, after some trial and error, I figured out that we had to use the following drivers in the Pro Tools Playback Engine settings.
If using the TASCAM input device, select the US-366 driver option under Setup>Playback Engine. Do this after booting up Pro Tools but BEFORE opening a session, since it will force PT to close down and require rebooting for the new setting to take hold.
When not using the TASCAM, then select the ASIOdirectX driver driver option under Setup>Playback Engine. Do this after booting up Pro Tools but BEFORE opening a session, since it will force PT to close down and require rebooting for the new setting to take hold.