Adobe Acrobat Reader X is not playing well with Dragon NaturallySpeaking v11 & Dragon Medical v10.1 these days.  If you have recently started receiving this error message, it was most likely caused by the recent Adobe patch.  Basically, you have two options:

1.  Open Adobe Acrobat Reader X, go to the Help menu, select [Check for Updates]. Download the latest update patch for Adobe Acrobat reader X (10.0.1) and install it.  In some cases, this update seems to fix the problem. However, it only seems to fix the problem for Dragon NaturallySpeaking version 11, it is unknown at this point whether or not it will fix the problem for previous versions of Dragon. If this doesn’t correct the problem, try the fix below.

2.  Completely uninstall Adobe Acrobat Reader X. If you need a PDF reader, I recommend Nuance’s PDF Professional.  Another good alternative is Nitro PDF Reader, which can be found online.

Verification Source:  In-House Testing & Chuck Runquist