Photos in library changed and unusable

Hello, I hope somebody can help me. I have a G4 dual 867 running 10.4.10 and Iphoto 5.0.4. What has happened is I have two hard drives.One had Iphoto 4 and one had Iphoto 5. On christmas Eve I was loading some photos on a usb stick to put in a picture frame. Iphoto brought up a window saying I needed to upgrade my photo library to work with the new version of Iphoto. I clicked on OK. That was a mistake. Now when I view my photos at more than half-way on the slider the photos grey out.When the slider is down, I can see them fine.I getinfo on a picture and it says 0 pixels by 0 pixels.The pictures seem to be in the iphoto library but I am concerned.I have 4000 photos of my kids growing up and Idon't want to loose the ones that are not backed up. Any help would be VERY appreciated.

Thank You Dave