Events and albums have dotted lines and do not display when cursor drags across thumbnail. Open events albums to full screen and photos visible. I had upgraded to iPhoto 11, but problem was not immediate. How to fix AND what caused it so can prevent recurrence? (iMac)
iPhoto '11, Mac OS X (10.7.3)
Back Up and try rebuild the library: hold down the command and option (or alt) keys while launching iPhoto. Use the resulting dialogue to rebuild. Include the option to rebuild the thumbnails. It can take 3 or 4 goes for this to work
As of iPhoto 9.6.1 this was still an issue for me and i finally found a "safe" way to fix this problem!
1) select thumbnails that show up as empty dotted lines. or select all thumbnails with command-a
2) click command-r 4 times. after the 3nd time the thumbnail will appear and the last click will set it back to how it originally was.
iPhoto 11 dotted line thumbnails, no image
