I have just run into a similar issue. On a Mac Pro running Lion 10.7.4 and Premiere Pro CS6 6.0.2, footage is displaying in the program and source monitors with really bad interlacing. It also transfers to exported footage, too. I have AVCHD footage, and the same footage converted to ProRes (HQ) and it’s doing the same thing to both files. What’s odd is it just started doing this. I have a project I edited a couple weeks ago and it was fine when I edited it, but when I opened it yesterday it was displaying this field issue.
I tried opening the same footage on my laptop (MacBook Pro 2010 running Snow Leopard) in Premiere Pro CS6 6.0.1 and the problem is not there. I am wondering if this has something to do with the 6.0.2 update on a Mac.
I also tried opening the footage on a PC running Premiere Pro 6.0.2 (Windows 7, 64-bit) and the problem is not there.