I am getting the same error message on QT movie files in iTunes.
I've tried your 32-bit mode tip (which I had forgotten about) and it no longer works for me. (using iTunes 11.4 on OSX 10.9.5) I get a message that says iTunes requires 64-bit mode...and then explains how to uncheck 32-bit box.
So I'm stuck.
I have noticed that it is QT movie files that don't play. In the INFO window of the QT movie files in iTunes they only have: Kind, Size, Bit Rate, Date Modified, Plays, Last played, and Volume. While MPEG-4 movie files have all of those fields listed as well as fields on the right of the window: Profile, Chennels, Video Dimensions, Total Bit Rate, Video Codec.
I've read that I can open QT movie files from finder and allow them to "convert" upon opening and then import that converted file back into iTunes. That sounds great. But I have over 10,000 movie files.
(this is frustrating because QT and iTunes are both native on OSX and have worked together in the past).
If you have any input or suggestions I'd really appreciate your insight.
Thanks,
CW