I just tried it on my system and the same thing happened, so it is probably a 10.5.2 problem.

The film and stage plugin was written for sketchup 5 and does not install directly into sketchup 6, but it does work once placed in the right folder. I you have previously installed it look for 2 things, a file called camera.rb and a folder called Previs. They would be in Harddrive/Library/application support/Sketchup 5/Plugins. to get the camera package to work you need to move those 2 items to Harddrive/Library/Application Support /Google Sketchup 6/sketchup/plugins. Once you relaunch sketchup you will have all the film and stage cameras in the bottom of your camera menu.

 If you want the components that come with the package you can drag the film and stage component library from the sketchup 5 components  folder and drop them in the  Sketchup 6 components folder by following the same path. 

If you do not have an installed version of the camera plugin in the sketchup 5 folder email me at david@go-2-school.com and I will send you the files.

David