Right now I'm trying to get Stage to open a Powerpoint presentation and the error messages I get are "invalid file format" and "file not found" (!) when I try to open it. Can anyone tell me why it might be doing this and how to fix it?

Hello,

Where do Stage comes from ? package of your distro, rpm, ... ? Or did you build/compile it ?
To import powerpoint files, you need to install/compile some filters. Did you ?

With these informations, we'll be able to give you more feedback.

Jean-Nicolas