Quicktime 10.2 quality settings

Hi,

I have a Mac Mini running Mountain Lion with Quicktime 10.2

I'm having a lot of trouble getting Quicktime to record video (New Movie Recording) at Medium quality. High quality works fine but make files that are too huge so I don't want to record that way.

What possible reasons could there be for the High quality setting to work, but the Medium setting to not work?

Thanks,

-Matt