I'm having some performance problems with PM when compared to previous versions. I'm using version 4.6.3 on an Imac 2ghz intel core 2 duo with 4gb of ram. I tried 4.6.4 and am having the same problems. Even in small folders of RAW CR2 files it takes quite a long time to generate the thumbnails. The bigger problem for me though is the long time it takes to rate individual photos - as long as 5 seconds per file. Moving through the files individually goes quickly unless a file is rated - that is when I get the spinning beach ball, around 5 seconds every time. Thanks.