How do I see the thumbnails in iPhoto now that I've moved my library from my internal drive to an external drive?

I'm wanting to move my iPhoto library from my internal drive (MacBook Pro) to an external drive (Seagate 1TB Backup Plus). I've copied it over and have redirected iPhoto to open from my external drive with no problem. However, now that it's opening from my external drive, all of the albums in iPhoto are black. I can no longer see true thumbnail pictures. When I double click on an album to view the pictures, all of the thumbnail pictures in the album are grey with a white dotted outline. If I scroll through the pictures, the actual picture does briefly pop up. When I click on an individual picture, it opens black.

I recently had to replace my hard drive after the first one crashed. I had no problem keeping my iPhoto library on that hard drive. So, I'm stumped as to why I'm having these problems now. Please let me know if you have any ideas!

I have iPhoto '09 v.8.1.2

Thank you!