Question about Vizio SV421XVT 42 in. LCD TV

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TruSound feature does not work

I just purchased the Vizio SV421XVT TV and noticed that the audio varies greatly from channel to channel as well as from a program to commercial. This problem seems to be worse with the TruSound feature turned on. With the TruSound feature off the audio works just like our crappy old TV that does not have any sort of sound level regulation.I have contacted Vizio about this problem but no joy yet. My TV is currently connected to a DishNet 522 DVR as the secondary TV, this means that the connection to the TV is via a coax cable to the TV's CATV port. Vizio support asked me to try another type of connection such as Component inputs or HDMI but that won't be possible for another week or two. I also connected a Sony Blu Ray DVD player to the HDMI port and noticed some sound level inconsistencies there as well but at the time I attributed this to the movie that I was watching.
I'm not sure if Vizio has a problem with their TruSound feature or if I just happen to have a lemon...

Thanks in advance for any assistance that you can provide,

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