Dropped frames

[kidevil]

I'm using DVD2AVI to encode Final Fantasy. It is 29.97 fps and the first few seconds come up as interlaced NTSC video, then switches to progressive FILM xx%. The % start lows and works its way up as it encodes. I encoded this once before in the exact same manner and it only dropped less than a second of video (24 frames). Now it's dropping about 1/3 of the frames. I am using IEEE-1180 iDCT, no field operation and YUV colorspace. I am not processing audio with it. What is causing it to now drop the frames?