It would be helpful if you could include the error. Also what version of IE and Adobe? They recently released an update a few days ago so I would try updating that and see if there is any change.

By the way, this is a known issue. IE9 being unable to open PDF files with Adobe Reader X. I think the recent update fixed that.

If that doesn't resolve the issue, Open Adobe Reader>Go to Edit>Preferences>Internet>Uncheck Display PDF in Browser

Sandeep Luthra | LTMedical.net
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