Background on me, I've worked in IT for many years (built my first PC 13 years), so I know my way around a PC.
I believe its something with the 608, see "what I've tried."
*ASRock A75M motherboard
*AMD A4-3300 CPU
Playback of video (streaming or local) appears to be jittery with lots of slicing (exacerbated when the camera shifts, or people on the screen move quickly). Nothing changed (software or otherwise) from when it was working till it wasn't. It was working fine, shut down, a few days later it wasn't working right.
What I've tried
*Uninstalled codecs (K-Lite Mega)
*Completely uninstalled video drivers, rebooted, installed again.
*Checked running processes, nothing taking up a lot of resources
*Disconnected from the 608, ran straight to a different HDMI port on TV...it works fine running straight through
*Tried another HDMI input on the receiver, issue returns.
*Shut down and unplugged receiver, issue persists.
My cheapo Sony BD player runs through the 608, no issues.