Hey LL928,
i had this same problem, and what it turned out to be was my upgrade to QT 7.1.5!
what is happening is that the resolution is all there (1920x1080) but that QT is diplaying the video @ 1888x1062. this is because of the aperture of the file.
if you open up Quicktime and choose: Window > Show Movie Properties and you select the name of your file, without the checkmark and you finally click on the Presentation tab, you will see that of the five possible check boxes, that they will be all checked off except for the last one: Conform aperture to: and in the drop-down box, Clean will be choosen.
what is basically hapeening is that QT is removing all the blanking information and providing you the equivilant of Video safe!
i have contacted Apple about this, since it seems to be a univeral fuction, and if you deselect "Conform aperture to..." you have to save out yoru file again as a self-contained *.mov.
to be honest, Apple wasnt really helpful and didnt know what i was talking about. this only happened once i updated my QT player also, because on other, non-upgraded boxes, i dont have this problem.
hope that helps some...
Mikey M. 🙂