I'm no expert, just a customer.
I have had issues in the past (not with this site though) in opening pdf's. In my case it was because I have acrobat 9 pro on my computer. acrobat and my browser would fight over what program opens the pdf....then crash. The way I fixed it was to go into acrobat...somewhere in the preferences I believe...and set the browser as the default to opening pdf's when applicable. Maybe this will help, I hope