CICOAlreadyCheckedOutInSameSession trying to update data in ProjectServer

Hi!

Guid iSession = new Guid (); 
w.CheckOutProject (projectGuid, iSession, SESSION_DESC); 
  w.QueueCheckInProject (jobId, projectGuid, false, sessionGuid, SESSION_DESC); 
w.QueuePublish (jobId, projectGuid, true, SESSION_DESC); 

The second day of digging but sensible Inet's nothing ... 

Project Server 2010

Error takes PSCLientError Output: CICOAlreadyCheckedOutInSameSession 

Thanks for the help!