I've gotten that as well, running iTunes 10.6.1. Unfortunately I don't remember if that happened before or after I switched to Mountain Lion, but I think that it was after.
Now I have to work backward within my line of experiences, so since I don't remember having that happen in DP2 (which I'm still running now), it must have happened in DP1. Therefore, I would attribute the problem to Apple messing around with QuickTime's underpinnings.
BUT you say it's happening in 10.7.3, so that sort of rules that out.
Let's narrow it down further. Is the video you're playing your own content that you've either ripped or downloaded and put into iTunes, or was it purchased from the iTunes Store?