[Josh Zacharias]

It is related to how you name your photoshop files. Your files names probably look something like:
scene 1.psd
scene 2.psd
scene 3.psd

When you import photoshop “scene 1.psd” after effects thinks its a sequence. Just uncheck the “photoshop sequence” option when you are importing the file.

If you try importing a photoshop file called test.psd suddenly your layers are flexible and you can drag the duration because AE didn’t check the “photoshop sequence” option automatically this time. Soon as your file name appears like a sequence numbering system. AE checks “photoshop sequence” automatically. Simply uncheck it before you hit import.