Are you using a Matrox card?
Matrox use upper field for PAL DV (lower for NTSC). I had a load of grief when I switched to Matrox from Canopus (who use lower for PAL) – suddenly all my AE work and stock footage was jittering all over the place.
I don’t think Magic Bullet actually analyses the footage for field order – it just looks at the file and asssumes that all DV is lower.
Matrox say that upper field for PAL is the spec laid down in the ‘blue book’ and that they have no intention of changing their drivers.
So much for standards…