Had to start a new post - the above was getting too long:
Grey Bars above/below HD channel images
Do you always have Grey (or sometimes Black) bars above and below the HD channels?
If you do, this is because you are sending a non-HD signal to the TV. This is either because you have used an incorrect connection - either RF-coax, composite video or S-video, or because you have improperly set up the STB to output 480i/p for all channels.
Set up the STB properly and while troubleshooting ensure that you remove all connections except for component video or HDMI/DVI.
Also, make sure you're on the correct TV input. Sometimes people will connect via S-video for the SD channels, but then forget to change inputs back to the HD cable for the HD channels
More on DVD Aspects:
Some TVs have an "auto-stretch" mode, which attempts to properly stretch incoming signals, however, it doesn't always work properly and non-anamorphic DVDs may not be properly stretched on most "auto-stretch" TVs. You either need to turn off "auto-stretch" or override it.
Now that there are many people using upconverting DVD players, or BD players, most HDTVs cannot properly stretch 720P/1080i signals, so the TV uses the "full" mode regardless of the original source material. This mode is usually correct for anamorphic DVDs, however, it is not for non-anamorphic DVDs, therefore you will need to feed the TV a 480i/p signal to allow the TV to properly stretch these DVDs. Many upconverting DVD players have a user selection for "4:3 DVDs" which you may also use to properly view non-anamorphic (4:3) DVDs - what this is called will vary with the player - it can be called things like 16:9 Wide, Wide, etc.
Note also that DVDs (movies) come in a huge variety of aspect ratio. Although the majority are 1.85:1 or 2.35:1, there are lots of other aspects from 1.1:1 to 2.8:1. See the following:
http://www.imdb.com/Sections/DVDs/AspectRatios/ (Dead Link, Sorry)
More on Studio Aspects:
The studios will often release different versions for the HD channels. If the original aspect was 2.35:1 for example, the studio may release an additional 1.78:1 aspect version for the HD channels to eliminate any black bars (which many people hate or do not understand). Most times when this is done, the sides of the movies are cropped and you lose some of the movie. In rare instances, they go back to the original print and "add in" information above and below the original aspect to create the 1.78:1 release, so you actually see "more" than the director intended. Sometimes the director had different aspects intended for various parts of the world and also created several different versions himself.