User xxxxxxxx is currently publishing to this folder
The following message is generated at the start of Publishing:
User xxxxxxxx is currently publishing to this folder. Try again after this user finishes publishing or publish to a different output folder.
You are attempting to publish to a specific folder that another user is already publishing to. When UPK starts publishing, it creates a 'lock' file called publishing.lck in the target folder (selected during publishing. When publishing completes, this file is deleted. The file contains the User ID of the user who is currently publishing.
Wait until publishing has finished. If this user is you, then make sure you are not already publishing from another UPK instance (for example, on a virtual machine). If publishing actually failed (for example, due to a connectivity issue) then you can try deleting the lock file (you may need to reboot the server (containing the folder) to terminate the publishing process.
If you used a remote connection (e.g. Terminal Server) to connect to another machine from which you initiated publishing but lost your connection, then log back on to the remote system. You will probably be connected in a new session, but if you go to Windows Task Manager and display the active Users, you should see your previous session, but listed as "Disconnected". Right-click on this and select Reconnect from the shortcut menu, and your old session will be reinstated. There may be a message indicating that UPK encountered an error. Click Continue and you should be able to resume where you left off.