preview with light or shade editing function is not working (black or white picture)

Hello!

I have a problem with the preview function in iphoto (version 9.4.2 on a white macbook, mid 2007, os x lion, latest version, 4 GB RAM, 500 GB HDD).

Whenever I use the light or shade editing function, the picture in the preview is getting completely black or white. If I close the editing screen, the normal preview is working with the edited picture.

I repaired the iphoto library, I tried to reinstall iphoto, I did a SMC reset but nothing worked. Yesterday, reinstalled my complete system and reinstalled iphoto but even this did not work.

Has anybody an idea how to deal with this problem? Is there a kind of BIOS funktion to activate or to deactivate like graphics boost or something like that? It would be great if anyone has an idea because editing photos efficiently is hard with my problem.

Thank you very much!