I am rendering a scene containing several models and an image sequence layer that contains 480 frames. The image sequence I've imported into the choreography consists of 480 images.

When I render in shaded mode, either as a QuickTime movie or as a jpeg sequence, the image sequence layer renders properly with each frame containing the appropriate image to create the illusion of seamless animation. However, rendered to final output, there are random frames which render what seams to be the 1st frame of the image sequence randomly so that the rendered .mov file and/or the jpeg sequence animation contains jumps (just from the image layer). It doesn't repeat back to the beginning of the sequence, it just sticks in the initial image from the layer randomly).

Other than the image sequence, the rest of the scene renders correctly in final output.

Any idea what's happening and how to address this?

I'm not sure of your setup here (i.e. Did you use patch images to frame the 480 images?)
Perhaps you have those patches' normals flipped and the backface culling setting is turned off allowing the image to effectively disappear during part of the sequence? (Even as I'm typing I don't think that is your problem)

There are several things it could be (doubled up patches at those areas for instance) or the setting of a decal that changes from Color to Transparency or another Type of Decal.

There is not enough information to go on at this point.

If you can post a project file, image or animation with the behavior that'll help clue us in.

do the images all have the same number of digits in their number?

If the images all have the same number of digits, like Robcat asked (009.jpg, 010.jpg, 011.jpg etc), maybe try animating the frame property for the decal in the chor.
In the chor, click on the "show more than drivers" icon beside the model shortcut.
Drill down until you get the to the Frame property for the decal.
On frame 0, enter 0 for "frame".
On frame 480, enter 480 for "frame".

If you end up creating more than two keyframes...
Select the "frame" channel and switch to the curves editor.
Select all the keyframes for the Frame property and double click in the selection box.
For "Interpolation Method", choose Linear.

Yeah! That seems to have solved it - thanks, Holmes and to all for the quick responses.

It's a mystery to me why the keyframe property edits would not be necessary when rendering in "shaded" mode, but then, many things in life are a mystery to me.