Indeed; this only manifested with live TV playback using W7's Media Center. All other AV sources played back through Media Center, Media Player, or anything else were perfectly fine.
About 30 hours on since I performed the BIOS tweak, all has remained fine; the media server continues to stream live TV without breakup - and for the hell of it in parallel with my test of it looping two HD movies over the Cat5e network to separate laptops.