Toon Boom changes frame rate from an imported video. Help.

Im making an animated videoclip, so I need to sync up the animation with an imported video I use for reference.

The video is in 24 fps, the toon boom project is in 24 fps too. The format of the video is . mov, 720 x 480 DV DVCPRO NTSC, Linear PCM, Timecode, and the colour profile is SD 6 1 6

When I play the video in VLC or Quicktime the sync is perfect, also I import the video in Adobe Premiere too and I dont have that problem neither, but when I import it in Toon Boom and play it, the audio sounds great but the frame sequence that toon boom create from the video is slower. I can see how every 4 or 5 frames the frame is mixed with the following, like the same effect of a interlaced field order. I attach a capture of the problem.

Thanks to all of you.

Please post a link to the movie so that I can test the import.
Had you changed the frame rate of the Harmony project at all?