The fix for 6647406, which involves pumping fewer Windows messages while LiveConnect calls are in progress, is causing browser hangs in conjunction with SSV dialogs. On earlier JRE releases, the AWT ModalityListener interface, which we use to detect the raising of modal dialogs, is not available. If an applet is run on a JRE version prior to the security baseline, a security dialog is raised, and the browser initiates a LiveConnect call (which is common when clicking on the applet in IE), then because of 6612243, we won't detect the raising of the security dialog and won't change the message pump running on the browser side to start pumping input messages. This will prevent the user from ever clicking the buttons on the security dialog to dismiss it.
This issue was discovered while investigating a problem report from ###@###.### regarding a failure to verify the fix for 6657990, which has been filed as a separate bug, 6661130.