Photos and still stretching when rendered, 1080i HDV

Hey gang,

I am currently cutting an hour-long doc for South African television. The footage and sequence is all 1080i (1440x1080, rectangular pixels i believe) HDV. I have edited countless projects in DVCProHD, but have never really worked with HDV before and I was wondering if anyone might be able to shed some light on an issue I am having.

When importing .tiff files and dropping them into the timeline, they act normally. I can blow them up, crop them, color correct, etc and they always display fine. However, once I render them (the dialog box reads "Conforming HDV video" rather than the normal "writing video") many (but not all) of them end up being extremely distorted, often much wider than they should be. If I then place text on them or alter them in some way, they go unrendered again and display correctly.

Any ideas? I have a feeling its something simply I am forgetting to do, but Im having trouble narrowing it down since its not every .tiff that has issues. Does it have to do with square vs rectangular pixels? Is there a photoshop step I am missing before importing?

Thanks very much in advance,
Daniel