Problem with short pauses during playback

[Old Jay]

I've been struggling with this issue for awhile now, and nothing I've tried has fixed it. When viewing either live or recorded TV, the video sometimes pauses for 2-3 seconds and then continues. The frequency seems to increase the longer I watch. Audio continues to play fine during the video pause. I can rewind and play through the same portion of the recording just fine, so I don't think there is an encoding/recording issue. The other day, I also noticed that the fan on the video card was spinning down during the pauses.

Here's my hardware set-up:
AMD 4850e CPU
Gigabyte 780G motherboard
Powercolor Radeon HD4830 video card feeding A/V over HDMI to my receiver
8GB RAM
WD 1TB GP hard drive formatted to 64k blocks (OS on a separate drive)
2x HD-PVR (C2 and E1) recording from cable boxes locked at 1080i output

and my software and drivers:
Sage 6.5 official release with the .33 beta demux (not running as a server or service)
Vista Home Premium 64-bit
Catalyst 9.1
Arcsoft h.264 decoder and AC3filter audio decoder, EVR video renderer


This issue has persisted through several versions of Sage 6.5 and demux beta versions. Switching from Catalyst 8.12 to 9.1 fixed some other very annoying playback issues I was having, but not the random video pausing. The PowerDVD h.264 decoder had the same issue, but slightly worse in that the video was very choppy for a few seconds following the pause.

I'm out of ideas, and this isn't helping the WAF. What am I missing?