Have you done the typical troubleshooting---ruling out obvious things like ground loops, sources, etc?
I'd start by disconnecting your HTPC (actually disconnecting the hdmi cable if that's how you've got it hooked up), try a different source (blu ray or dvd player?), projecting a white field from a test disc. Then also the white field from the HC3800's own white test screen.
And if waves still persist, lift the ground pin of the HC3800's AC cord (with one of those hardware store adapters). If the waves go away after that, then you have a ground loop.
If not, and you still have waves on white fields from test discs on different sources (HTPC, DVD/Blu players, etc) and the HC3800's own white test screen, then I think it's time to call Mits Support

(also make sure to rule out hdmi switchers, AV receivers that might be in the path by connecting your blu/dvd players direct to the PJ)