When the ULC system stops working, stops with a Debugger window, or just will not stop, you can reset the system. From the System Transcript window, select ULC->Debug->Reset Ulc System. In response to this selection, all active ULC contexts stop, and all open communications are ended. ULC Monitor should no longer list any open connections.
ULC->Debug->Inspect all Ulc Instances provides verification of a cleaned-up image if it lists only these instances:
Any application-provided objects and all instances of UlcAbstractView subclasses still visible after the reset constitute a potential problem (runtime memory leak in ULC servers). The causes should be investigated and eliminated. Causes for hanging instances are known to include references to the object from some global object; start looking for those first.