Forgive me if this has been mentioned before, but a lot of my established screen savers don't work under Leopard.
I went from a G3 to an Intel iMac, and most of them stopped working. I get an error message that they are incompatible with this version of OS X, and to please contact the software maker for an update.
Now, I know you're thinking that the reason might be that they were made for very old computers like my G3. But one screen saver is copyrighted 2007, so it can't be that behind the times.
I tried to reinstall that screen saver from the software maker's site, but got a -5000 error message.
I know these are just screen savers, but one in particular is actually a cute mini-app that my granddaughter loves, a children's game. I'd love for her to be able to continue to play it.