[asterisk-users] ring group failure with "ExtensionState: 4"

[asterisk at newkirk.us]

New installation from AsteriskNow 3.0.0 with asterisk 11 and freepbx, 
running Digium D40 and D70 phones.

Direct-dialed extensions work fine, but extensions in RingGroup won't 
ring - dialparties.agi apparently removes them from the dialstring 
pre-emptively:

 dialparties.agi: EXTENSION_STATE: 4 (UNKNOWN)
 dialparties.agi: Extension 2010 has ExtensionState: 4

What can I do?  Any extension that is actually registered and 
available is being removed, then the ring group drops through to 
'Destination if no answer'.  I've got a town hall waiting for this 
system and I've never seen this problem before.  Googling finds a few 
people with this problem, but I've not found a solution posted 
anywhere yet.

j