Some time ago i noticed that when I opened a PDF file, Adobe Reader X stopped responding for sometime. I noticed it happens on Windows 2003, Windows 7 and Windows 2008. after some investigation I found a solution in disabling Adobe’s “new” Protected Mode feature. Open Adobe Reader X navigate to Edit->Preferences->General clear the check-mark at “Enable Protected Mode at startup” Click OK to save the changes (acknowledge the warning) Shutdown Adobe Reader X You can also disable protected mode through a registry key [HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Adobe\Acrobat Reader\10.0\FeatureLockDown] “bProtectedMode”=dword:00000000 source: http://www.efferen.nl/2012/03/solved-adobe-reader-x-hangs-after-opening-a-pdf-file/http://www.efferen.nl/2012/03/solved-adobe-reader-x-hangs-after-opening-a-pdf-file/