DSP 3 causes a miscount in fields after muxing my project, How???

Out of the blue my 3.0 version of Dvd studio pro muxed a dvd (the TS folders onto my harddrive) which has a miscount in fields. The exported Dvd files result in an image that is typical for the mix-up between the lower field of one frame and the upper field of the other, instead of the right combination of a lower and upper field of one frame to build the image.

Does anyone recognise this problem and, is there a sollution to it? Here's the setup I always used without problems until today

Here's my setup: I import dv files via firewire into i-movie (because my Media 100: 844/X system cannot export good DV-files - don't ask why...), in i-Movie I choose the quicktime-advanced export option and choose 'Mpeg 2 for Dvd' to get the '.m2v and .aiff' files.
To deliver my clients a copy of our production for them, I've made a template for Dvd studio pro that I always use. A simple one-button menu plays the contents from Dvd. As I said - I never had problems until today.