Double-clicking on the 'Pins..' or 'Initial Contests..' buttons in the CORE Generator Core GUIs (including the Virtex Block Memory) may cause the GUI to hang on some workstation platforms.
Solution
The only way to exit out of this condition currently is to kill the CORE Generator 'JRE' process.
As a preventive measure, since these buttons only require a single click to activate them, try to avoid double-clicking on them if at all possible.