interactive zoom not working

[kimorrell]

If I activate the interactive zoom on a small wmv clip it works fine.
But I am trying to use VLC to view HD video in an extremely large file (225 GB), and it simply does not give me the onscreen zoom controls. I am wondering if there are any file size, resolution, codec or other limitations to being able to view the video in interactive zoom. The other strange thing is the audio does not play in VLC (it does play in quicktime); this is not a huge deal as I am not using the audio at all, but it may be a clue as to why they file won't zoom. The file was captured from HDMI video at 1080i with a Blackmagic Shuttle Hyperdeck. I will change the output next time I record to 720p, but I want to figure this out before I do that.

Video info:
Codec: DNxHD (AVdn)
Resolution: 1920X1080
Frame rate: 29.970029
Decoded format: Planar 4:2:2 YUV 10-bit LE