Agent 2471 is logged in with channel ID SIP/hq-ast-v06-user-00004142. Something happens that disconnects this channel.     Agent tries to log back in getting channel ID SIP/hq-ast-v06-user-000043ef.    The AGENTLOGIN event happens at the exact same second as the AGENTLOGOFF event from  SIP/hq-ast-v06-user-00004142 and more importantly the AGENTLOGIN event was first in the debug file causing me to believe it was processed first.   The agent never actually connected/logged in with SIP/hq-ast-v06-user-000043ef  and the channel just keeps getting/sending HANGUPREQUEST events.   At this point the agent keeps trying to login and get the "agent already logged in" message, thus  Asterisk believes Agent/2471 still exists.
				
				[Dec  3 09:10:36] DEBUG[28088] manager.c: Examining event:
				Event: Agentlogin
				Privilege: agent,all
				Agent: 2471
				Channel: SIP/hq-ast-v06-user-000043ef
				Uniqueid: 1354547413.31185
				[Dec  3 09:10:36] DEBUG[28088] manager.c: Examining event:
				Event: Agentlogoff
				Privilege: agent,all
				Agent: 2471
				Logintime: 3950
				Uniqueid: 1354543471.29911



This call came  into the queue (SIP/hq-ast-006-user-00004440) and tries to connect the call to this agent that Asterisk thinks is still there:

				[Dec  3 09:14:59] DEBUG[7566] app_queue.c: It's our turn (SIP/hq-ast-006-user-00004440).
				[Dec  3 09:14:59] DEBUG[7566] app_queue.c: SIP/hq-ast-006-user-00004440 is trying to call a queue member.
				[Dec  3 09:14:59] DEBUG[7566] app_queue.c: Trying 'Agent/2471' with metric 1001003
				
It can't connect and then continually sends/gets the HANGUPREQUEST event.  We can't kill this channel via the CLI either.

I am guessing that the queue algorithm  just keeps trying to connect this channel, leaving all future calls to always be waiting in the queue.

FYI - We are unable to destroy this channel via the CLI.

NOTE:  If the AGENTLOGIN and AGENTLOGOFF events came at the same time but the AGENTLOGOFF was first, there were no issues.