Kirk,
What I'm saying and what I was experiencing on the two Macs was absolutely no thumbs for a long while but an unhealthy spike in CPU usage. When I clicked an empty JPEG thumb I got an empty image space. Then navigated with the arrows left and right, still no images show up. Exit by way of Ctrl+W. Still no thumbs but CPU at 100% 100%. Then perhaps after 60-120 secs the thumbs slowly emerge and I can click them and view them but it is all sloooooow going.
Exit PM, start up again. Same sorry story. Exit PM, exit Mac OS X, restart computer, fire up PM 4.5.3. Same tale. Then only solution: Re-install 4.5.2 and peew... everything is back to normal: Swift PM startup, no thumb trouble or anything. Low CPU usage.
Frankly, I am surprised this happened on two different Macs. And I am now actively working with client files on both computers running PM 4.5.2 without a hitch.
I posted this major problem also on the Danish site for press photographers but it seems like I am alone with this problem as of now... Go figure
Best,
Morten Vassing
P.S. Not really a beachball spinning but really bogged down system reply and yup, only JPEGs that work like a charm on 4.5.2.