Safari with OS X 10 6.8 will not open PDF files After installing the OS X 10.6.8 update on my iMac (10,1), when PDF files are opened within Safari, a blue circle appears, then a black screen with the first page of the PDF file. It will not open further or download.

I also downloaded the update on our older iMac (7,1) and the same thing happened.  After visiting the Apple Store today, it was suggested that we reinstall Safari, which we did on both computers.  This did not change the situation.

We also have a third computer, a laptop that has not been updated to 10.6.8. This computer has no problem.  Any ideas?
Run the installer for Snow Leopard over your current installation.  The issue is in your settings.  The easiest way to make this work is to let the installer reinstall.  Most likely you restored both machines from a time machine backup at some point and the setting was incorrect and never got fixed.  Easy fix though.