Re: Acrobat Reader XI - constant crashing

Three things you can try...

1. Using Windows Explorer navigate to C:\Program Files (x86)\Adobe\Reader 11.0\Reader, then double-click on Eula.exe and accept the license agreement
2. Can you open Adobe Reader by itself?  If so, try disabling Protected Mode [Edit | Preferences | Security (Enhanced)].
3. It could even be a malware issue; see http://helpx.adobe.com/acrobat/kb/reader-core-dll-error.html

If you want to go back to Reader X, uninstall XI, then download and install version 10 from http://get.adobe.com/reader/enterprise/