Clip quality severely degrades when imported into Premiere Pro CS5? (appears interlaced) I have a clip which is 720p30 and plays back perfectly smoothly when opened outside of premiere. When I import the clip into premiere and play it back it looks awful: http://imgur.com/JHVbl

If I export the sequence it looks the same as in the preview (interlaced and awful).

Premiere indicates that the clip is 1280x720 (1.0) which is correct and the sequence preset I am using is AVCHD 720p30. I have tried fiddling with interlacing settings (though none should be necessary) to no avail.

I have a project full of different 720p clips from different sources and this is the only one that is exhibiting this behavior. The problem clip was generated by another program.

Any idea what I'm doing wrong?
The problematic file could have been encoded using a different codec, which Premiere is unable to convert effectively. 

If the file looks ok in QuickTime player, I would export it to the same format as your Premiere sequence, and see if it looks any better when you reimport it into Premiere.