I am editing a film shot HDV 1080i. However, the Sequence and Viewer settings show it as 4:3 letterbox. The master clips are true 16:9 widescreen. Did I import them wrong, or can I somehow salvage my edits through XML or EDL exports into a correct Sequence setting?

This is about 2 months of work I am looking at here and I'd love to hear some good news.

Edit: The clips, when dragged into a correctly set, new sequence display fine. Therefore they were captured correctly.

You can select all the clips and drag all the clips to a new sequence with the right settings, or you can change the sequence setttings of the original sequence.

Depending on the specifics, will probably have to go through and change the motion settings of all the clips (Scale back to 100% and correct the Aspect Ratio settings), the solution is pretty straight forward (I assume you're referring to Final Cut Pro). If you have not applied other motion effects to clips, you can create a "Motion Favorite" to correct aspect ratio and scale and simply drag that to all the clips and thus correct the scale and aspect ratio of all clips and get things back to normal in one operation.

There's a Final Cut Pro preference setting to ask for the sequence settings evert time you create a new sequence, you might want to turn that on if you work with a variety of formats.