asterisk users - Jul 2006 - Unable to find extension in context ''

I'm getting this when I try and use the Asterisk #1, transfer feature:
Jul 17 15:28:42 VERBOSE[14192] logger.c:     -- Unable to find extension
'6' in context ''

Don't know why. How can Asterisk even have a null context? Where could that
come from?

Queue agents are trying to transfer callers.

My agentcallbacklogin command is:

Executing AgentCallbackLogin("IAX2/xxx.yyy.142.203:4569-4",
"80014054||80014054@one_callback") in new stack

and asterisk knows where the agent is:

hestia*CLI> show agents
80014054     (Customer Care Spare) available at '80014054@one_callback'
(musiconhold is 'default')

and my context one_callback has:

[one_callback]
exten => 1234,1,Answer              
exten => 1234,2,Wait,1              
exten => 1234,3,Playback(tt-monkeys)

exten => 80014054,1,Dial(SIP/80014054)

However, when the agent hits #1, followed by the a single digit '1',
asterisk immediately logs:
Jul 17 15:28:42 VERBOSE[14192] logger.c:     -- Unable to find extension
'1' in context ''

As I said, I have no idea how I managed to get an empty '' context.

Doug.