The "kind" field in several of the pictures in my iPhoto library is blank. I'm looking for ideas on how to fix this.
That just tells us what image format and extension the original file has. Select the thumbanil of the image without Kind and select Show File from the contextula menu. You'll be taken to the original file where you can see what its extension is.
It just means the EXIF field Kind for that image wasn't filled in.
The fact that it does't show the format doesn't affect its useability.