'IE cannot display the webpage' when opening PDFs

A number of my users are complaining ever since an upgrade to IE9 that when they click a PDF link, IE gives the error 'Internet Explorer cannot display the webpage' (ie doesn't even call Acrobat Reader add-in). I can view the PDFs just find in Chrome, I can download the PDFs and open them with Reader just fine, but IE gives me that error when trying to open the PDF link directly.

Where can I start? I've already seen the 'use FF instead' option so I don't need that :)


Known bug.

Microsoft Internet Explorer 9 was released after development for Adobe Reader X was complete. While we made every effort to anticipate the way the final release version of IE9 would behave, our PDF viewer plugin is not yet compatible with IE9. This is being worked on by our engineering department. In the interim, when trying to open a PDF file from the browser, save it locally to your computer and open it directly in Adobe Reader.

Moving forward, please continue to install updates to Adobe Reader X as they become available. When this issue has been resolved, it will be pushed via an update. Thank you,

David Acrobat Community Manager Adobe Systems

I've seen that this may be resolved by ensuring users are running the 32bit version of IE but YMMV.