Help! iPhoto no longer shows image thumbnails

I'm using iPhoto '09 v8.1.2 under Mac Lion OS v10.7.5 on a Mac Pro 1,1. I recently upgraded to a new hard drive, and nearly everything transferred over just fine, but iPhoto is not working correctly.

I get no thumbnails in the grid view, which pretty much breaks the app for me.

I have tried Apple's recommended fix of launching iPhoto with Cmd-Opt held down, which brings up the rebuild thumbnails dialog box:



I've done this a few times, but it does not fix the problem.

I can't navigate my iPhoto library without the tumbnails, and it's already messing things up for me. I make heavy use of Keywords and Names (which is why I haven't upgraded to a newer iPhoto) but they're useless if I can't see previews of the images when I search or try to manage my library.

Does anyone have any ideas to get preview thumbnails working again?

Thanks!