When I try to save a tab I get a message of "Unable to save the current tab due to it having been updated by...."
This is a feature of a database of this nature. If one user is editing (for example) a Job Header other users cannot perform actions that will also update the Job Header.
This can also be caused by a phantom connection to the server.
If the user named in the message is really logged in and has the tab open, then you will have to wait until they have finished editing the record (which the process you are in is also trying to edit before you can proceed).
If the user named in the message is not really logged in, their session will need to be aborted from the server.