QuickTime movie from JPEGs with specific durations

I’m trying to create a movie from a folder of JPEGs, and I need to set the duration of each image individually.

I can make a new movie, and I can add images individually, but I can’t set any durations, either of the movie or the individual images. When I add them, they are given a duration of 40 no matter what I do. When I play the movie, each image shows for less than a second. (I’ve tried changing the time scale, too, but no improvement.)

I also tried to create a track, since the QuickTime dictionary states that the duration of tracks can be set (as opposed to documents, where duration is read only). However, nothing seems to change, and if I try to get properties of every track, I get this error in the Event Log:

make new track at beginning of document 1
          --> last  <<class >>
get properties of last << class >>
          -->  error number -1700 from last <<class>> to reference

Any suggestions will be greatly appreciated, thanks.
BTW, I’m using QT 7.6.6 and OS X 10.6.4.