Dictation not working in OS X 10.8 Mountain Lion
I had the same problem and it drove me crazy! This helped me:


Go to ~/Library/Preferences
( &#x21E7;+&#x2318;+G )
Locate com.apple.assistant.plist and move it to the Trash
Open Dictation &amp; Speech preference panel, disable dictation
Reboot
Re-enable Dictation &amp; Speech.


Voila!

PS This hint has the nicest side-effect: In Mail, all accounts used to be offline after sleep (Small triangle icons next to account), and would only come back on after quitting and restarting Mail.app. Now, all is well again. Ts!