I'm trying to remember, but I think there was a weird issue with AMOS Pro and interlace screens under KS 3.1. Since AMOS banged the hardware pretty heavily, there are all sort of issue that pop up. I'm pretty sure that KS 3.0 worked fine, but once I upgraded to 3.1 interlace screens wouldn't display right.
I don't remember if there was a patch from Pietro Ghizzoni or if you had to flip back to Workbench then back to AMOS for it to show up right.
http://eab.abime.net/showpost.php?p=1169208&postcount=24 show's Toni Wilen's agreement with the situation.