themes invisible, blank pages, colours not right, looks like a graphic error, but isn't one

hey there

Keynote '08 (used on a 10.6.8 Mac OS X) doesn't work anymore. The only thing that works and looks as it should is the window itself with all the buttons and stuff.

I choose a theme and want to start working and all I can see is a blank page...no background,no letters etc.

I cannot see what I'm writing (cause everything's in white), only when I mark the letters I can see them. When I start the presentation I can either see nothing at all or a very ugly version of the theme and words, that looks as if the graphic card of my Mac had crashed. I cannot even choose different font colours...everything's just white.

Some of the themes appear....but a theme that's supposed to be in blue appears green....and so on. It's so strange!

Already finished keynotes can be opened with the app, but look the same. Everything looks like a graphic error so to speak. Pictures look as if they were a negative of the original picture.

The only way to look at an existing keynote is by using "preview" in the finder.

I've already deinstalled the software and put it on again.

Nothing changed...

I just don't know what's going on here....

Any ideas?? :-(