What digital box do you have? Do you have the new Navigatr guide on your box? AMCHD should be channel 482. Channel 32 should be AMC but it's auto HD, however if you want to check both channels (328 AMCSD and 482AMCHD), please check to see if you get a full screen on either of those channels.
Try the following:
Click Settings > Appearance > TV Type > 1080i HDTV
> Video Output > Normal
Also make sure that your TV picture size is set to widescreen (If you have a widescreen TV). Sometimes the settings on the TV itself may not be correct.