Picture Position with Dish HD

I just recenly purchased a Vizio 42" 1080p LCD HDTV and have Dish HD (VIP622 DVR receiver). I have noticed that the vertical position of the picture seems to be different with each channel. On some channels, I noticed these weird white bars on the top. They went away if I raised the vertical position of the picture. However, this will cause other channels to have the picture cut off a bit. Does anyone know why this is happening and how to fix it?

Also, closed captioning is not working, either using the Dish Receiver closed capion option or the closed caption on my television. I checked the info on several programs to see if they include closed caption, but it did not work.

Any help on these issues would be greatly appreciated:)

Have you noted anything in common with those channels that exhibit the white line at the top? Are they 720 signals or 1080i or SD? Is just on "local" channel content? Just on "national/network" feeds . . .
There can be various causes for this; same for the correction methods. The set may need an "overscan" adjustment-- not just "position" adjustment-- but if I had to guess, I would guess it it is not a problem with the actual TV.

I get the lines on one certain network channel on commericals that are in 4:3-- the actual HD 16:9 program has no white line at the top . . . It is not a problem for me.

a 1080 signal is actually 1088, but the bottom 8 lines are BLACK and this is for adjustment. Proper setting of the overscan and the vert. position should correct the problem you are seeing.

As for the Closed Captioning, I have no clue-- as I have never used these feature on my Vizio (or other HD TV).

Thank-you for the help. I see the white lines on both HD and SD programs. It just depends on the channel that I am on. I am not familiar with an "overscan" adjustment. What do you recommend for how to adjust the tv?