"Fatal Error - Acrobat failed to connect to a DDE" server on Acrobat X. I re-installed but no luck.

A suggested and workable solution seems to come from this topic http://forums.adobe.com/message/4665628

In which you have to go into the registry and doing the following:

We were successful to resolve the issue for Acrobat X by navigating to HKEY_CLASSES_ROOT\acrobat\shell\open\ddeexec\application and changing the Key "AcroviewA10" to "AcroviewR10.

try to change the similar key for Acrobat 9.

Please export the registry before making any changes to it.

I have the same problem when I try to open a PDF file with internet explorer. It says "The Acrobat/Reader that is running can not be used to view PDF files in a Web Browser." The error says it can't connect to a DDE server.

None of the "fixes" actually fix the problem.

Process explorer shows the Acrobat process running (multiple times if I've tried to open it multiple times) but none of them are visible in windows.

Acrobat works by itself on locally stored files.