I will mention this in case if might have any relevance. Using Elmer's suggestion, my PDF files were showing with thumbnails---until today!!! I did three things and I do not believe the first two would be related since your problem started before the updates were issued. Two Updates were installed, .net 3.5 for SP1 and C++ for SP1(SP1 was installed yesterday). I have looked at uninstalling them, but it does not seem possible. Also I changed this RAID setup from Basic Drives to Dynamic Drives. Why Dynamic Drives might be involved, I do not know, but whatever caused it, I can no longer get the PDF to show thumbnails on this x64 version. There is a chance SP1 is involved since I do not remember if I refreshed the Desktop after that install. My 32 bit version continues to work normally, but it does not use Dynamic Drives, so maybe that rules out SP1. If there is anything you want me to try, I do have a 32 bit system I can mess with. Edit: Looks like the possibility has not panned out. I am now able to change the Thumbnails even with the Dynamic Drives. I am working on one other thing, but it is also not showing consistency.