I'll jump in in the meantime to say I'm having the same issues, and have for some time. Initially I had the 800e connected to a Pentium 4 running XP service pack 2 with the latest video and pinnacle drivers. At some point I just gave up and connected a direct capture device to my cable converter.
After purchasing a new system (see profile) that can more than handle video streaming and live TV, I find that the issues I had in the previous system using Pinnacle's own software have carried over to the new system using the proprietary software as well as Windows Media Center. Launching the software results in perfectly synced audio, whether standard or high definition, but if I change the channel or simply watch for more than a few minutes, the audio slips out of sync, about 1 second give or take, and doesn't sync back up unless I restart the app (either WMC or Pinnacle). The same can be said for recording, but I could almost understand delays there, but not with live TV. The same can be said whether I'm using a coaxial cable connection or the included antenna.
My video card and audio drivers are as up to date as I can make them and the latest software (mentioned above) doesn't apply to my 800e, but I have downloaded the latest drivers found elsewhere on the site. I'm at a loss as to what to do further and have become disappointed overall in choosing this particular device. Additionally, I'd really like to start using this while I work, since I'm at the computer a good portion of the day and I would expect to be able to have it running while I'm working with other applications (with reasonable processor/ram load) without the audio delay.