When working on a multi-developer database with the Modeler, the messages you get mean that another user, let's say U, is currently editing the microflow. This locking-mechanism prevents you from making changes to a document that someone else is currently editing, which could cause data loss.
Sometimes it can happen that the lock on a certain document D remains even though user U has already stopped working on this document. If this happens, you can "steal" the lock from user U by opening D in your Modeler and making a change, or by choosing "Start editing" from the context-menu of the document tab. You will then get a pop-up asking if you're sure, because user U is still editing the document. If you click 'Yes', the lock of user X will be removed, and you will be free to rename or delete the document.
Try to open the model as administrator. Pre 3.0 versions could suddenly be in need of administrator rights for some reason.