I'm still getting glitches in my picture of freeview HD. Using very latest powerdvd8 codecs with 8500GT, which are workinning i'm pretty sure, so thats not the issue. Updated to Mediaportal RC4 which is running slick as, channel changes are within a few seconds.

To be honest the mediacentre has been rejected for TV watching for a long time (blame mysky, HTPC mainly movies + file server), ive just had it recording a series for future archiving and not watching.
But yesterday i was watching a program from the timeshift and i noticed i get glitches every now and then. Sometimes its very frequent, up to 3 times in 10s. Sometimes it'll go fine for 5mins before a glitch.
Also the magnitude of them changes, sometimes the audio continues and the picture freezes for a second, sometimes you loose audio and the picture goes blocky and unrecognisable for several seconds.

Reception problem?
The iDTV upstairs has zero issues with reception. Setup is a 91 element UHF which i know isn't aligned correctly (its facing upwards slightly and to the left too much, need an extended ladder to reach it), then to a masthead amp combining with VHF, through the power injector to a splitter, which then runs to each room. Minimum of RG6 dual shield, quad shield between the wall and HVR-2200. In between the tuner and 8500GT theres a plastic bag with tinfoil 2-3 thick, to block out RF interference.

Thoughts? Is it the badly aligned antenna, even though the other TV has zero issues?