I had the exact same thing with the same card. Very bad signal appeared to be the issue of the distorted image and sound.
Then I decided to put the same card in a Dell Vostro 200 machine -> all perfect! Same Ubuntu OS, same Tvheadend version, etc.
So I have
- system A: Intel DQ57TM with Core i5-650 - NOT OK: bad signal resulting in loads of "continuity counter error"
- system B: Dell Vostro 200 with Core2Duo - OK
All with the same:
- cables
- OS - both Ubuntu Lucid (+ v4l compiling) and Natty
- Tvheadend version
- Muxes config
- IRQ sharing
Now I am lost in what can cause this issue. I am certain it is something hardware-ish like a slightly different power on the PCI bus, grounding issues, etc.
Note: my TV connected through the card, no problem at all; stable signal there.