Agent unable to login to outbound campaign using OCS 7.6

[stevehaz]

We have an agent who is suddenly unable to log into a campaign. He can log in to softphone OK and can take inbound calls but cannot access the campaign. In OCS I am seeing the following:

Agent[874`Place_813738]::StatDispatch EventSessionStatus {
AgentSession[155`BRC_NCL@BRC_NCL_NCL_VAG]Running, assigned::EventSessionStatus {
Agent[874`Place_813738]::RequestDistributeUserEvent {
Agent[874`Place_813738]::send UserEvent, [color=red]no login DN available[/color]

We are using Avaya CM5 with TSAPI Tserver. Anyone seen this before?