In Microsoft Powerpoint 2007, I click on the animations button on the top part of the window. Then there is a place where you can click called animation and under it custom animation. I've tried clicking that animation once and used it only once before and I want to use it again, but for some reason I can't click it and I can't do any custom animations either.

Why is this?

you might of not clicked the shape before you pressed the button.