Since I installed Windows 7 I have not been able to read PDFs in IE8 - all I get is a blank page. I can open them fine when they are in a stand alone file. I have tried Reader 9.2, 8.1.3 and 8.1.4. I tried unchecking 'display PDF in browser' but that gave me an error message that the file could not be found. I have seen a number of posts on the internet but no solution.
I had the same problem but I use Firefox, so I went to top of screen in Firefox and clicked "tools" then "option" then under "applications" tab had to adjust for documents, forms etc...for Adobe Reader 9 to open documents and it worked. My issue was when online trying to open a pdf form or page and I would just get a blue box with a question mark. I am also on Win 7...not sure if this will help you since you are IE.