I have a Computerlounge HTPC : 

Athlon 2 X4 640
4GB RAM
Radeon HD5670 512MB
Hauppage Win TV-HVR-2200
Windows 7 Media Center

Works great for most things, plays COD Black Ops fine etc
Also works fine for watching Freeview, except for TV3, where we get occasional pixellation - just a small glitch / flicker / blocky area on part of the screen, then it will be fine for 2 or 3 minutes, then another little glitch etc etc. Tried all the obvious things ( replaced HDMI Cable, replaced Aerial Cable etc ).
Got a technician from Aerial Master out, he stuffed around, installed a signal Amplifier, picture seemed to be fine, so he left. But a couple of days later, same problem came back. Problem seems to be worse on cloudy / overcast days, even pixellates on TV3+1 occasionally.
But the other annoying thing is that the picture is fine on our other TV, which is also freeview via a Panasonic DMR XW380. We never have any problems with this TV, and it runs off the same Aerial ( via a splitter )
The guy from Aerial Master reckons the signal strength is the same for both TVs, he reckons the problem must be something to do with the HTPC ?
I really don't know where to start - send it back to Computer Lounge ?
Or does the HVR-2200 need a stronger or weaker signal than the Panasonic receiver ? ( I tried to update the drivers but it says I have the best drivers installed. )

Help please !