That is an interesting observation but my bottom line is that reverting back to avast 4.8 solves the problem which I've bee able to demonstrate on two different computers. So I am not sure what conclusion one can reach from your observations. I can not easily revert back to an earlier version of Adobe Acrobat Pro since the program installation is tightly controlled by Adobe and every time I've tried to deactivate the license, it has failed and then I've had to spend over an hour with the Canadians attempting to reload the program. I think that is because my program has been an upgrade since version 3. Another oddity that I 've mentioned before, is that restoring IE8 after it has frozen/hung/crashed resolves the problem. But I've noticed that when there were two IE8 processes executing prior to the IE8/pdf hang, after restoring IE8 (a nominal Microsoft option in IE), there are four IE8 processes executing after the restore(maybe two processes have only ceased grabbing the processor??). A number of weeks ago when I first reported the problem, numerous others reported the same problem but since then I've not seen any new posts on the problem. I suspect most users are so use to IE8 freezing they don't pursue the problem. Regardless, I am hoping that the next release of Version 5 fixes the problem since being able to view pdf documents on the Internet is a higher priority than just having the latest version of avast which is why for now I have gone back to Version 4.8 on one of my computers to circumvent the problem.