Are you getting the AssistantServices.framework bouncing in your dashboard when trying to use dictation in OS X Mountain Lion? This simple fix will get the framework to stop bouncing and for you to see the cool dictation box popup properly.
sudo vi /System/Library/PrivateFrameworks/AssistantServices.framework/Versions/A/Resources/Info.plist
Insert the following between row 4 and 5 (right after <dict>) :
Save the file down and you’re all set; double click your fn button and dictate away.