I tried the small power button - unfortunately it still flickers (more of an off/on thing than a flicker, really). I find it really bizarre that the PVR was working fine with the Denon and now the connection decided to go haywire. I'll have to try re-setting tomorrow. Wish me luck!

Thank you lgplasma for providing the power button suggestion. I rebooted the PVR (unplug the PVR for 30 seconds and then power back up) and that seems to have solved the problem.