Wait! Hold that beer shipment!
I just tried to change some images on my current editing project and - as soon as I select more than one, the Menu/Tools/Change Duration, dims out and becomes inactive.
However, when I created a new project, with several of the same images and video clips, the Change Duration menus remains enabled when I select several. I added sound and titles and it still remains enabled.

I don't know what is going on here.
I restarted VS 10+, repeated the same tests, and got the same results: only my current editing project has the problem.
Something is disabling the Change Duration menu. for that one project.
Edit: Using my test project:
When I select an image and a title, the ChangeDuration menu remains enabled but when I click, the dialog box does not open.
When I selected an image, a cross fade transition, and a video clip, VS crashed with error signiture AppName: vstudio.exe AppVer: 10.0.0.0 ModName: vstudio.exe ModVer: 10.0.0.0 Offset: 000a1b15
This is repeatable