I have a Zenith C32V37 with a QAM tuner internal to the unit. I think that Zeniths are made by LG..
I never knew that the TNT audio was on another channel. Rather than boxing like all the other channels, non-HD content on TNT seems to be squished.
Also, I just dropped "standard" cable (which we signed up for during basketball season and kept neglecting to drop). The PBS problem appeared before they installed the filter to block standard cable, but I didn't notice the NBC problem until after that.
I wouldn't really mind loosing the HD PBS, but, darn it, PBS is the best thing about Digital TV for us. And switching back and forth to get different channels over broadcast (PBS-HD, NBC) and cable (PBS-ED, PBS, PBS-NC, CBS) is a royal PITA with my Zenith.