Cannot launch CICS Explorer 5.2 !MESSAGE An internal error has occurred

Question

Why does a window pop up with "An error has occurred. See the log file at H:.zosexplorer.metadata.log." when I try to open CICS Explorer V5.2?

The last line of the log has the following:

!ENTRY org.eclipse.core.jobs 2 2 2016-01-08 12:56:41.849 !MESSAGE Job found still running after platform shutdown. Jobs should be canceled by the plugin that scheduled them during shutdown: org. eclipse.ui.internal.Workbench$54

Right at startup the log shows:

!ENTRY org.eclipse.ui 4 4 2016-01-08 12:56:38.656 !MESSAGE An internal error has occurred. !STACK 0 java.lang.NullPointerException

!ENTRY org.eclipse.ui.workbench 4 0 2016-01-08 12:56:39.185 !MESSAGE An unexpected exception was thrown. !STACK 0 java.lang.NullPointerException at org.eclipse.ui.internal.Workbench.createWorkbenchWindow(Workbench.java:1 236)

!ENTRY org.eclipse.osgi 4 0 2016-01-08 12:56:39.418 !MESSAGE Application error !STACK 1 org.eclipse.swt.SWTException: Failed to execute runnable (java.lang.NullPointerException) at org.eclipse.swt.SWT.error(SWT.java:4361) at org.eclipse.swt.SWT.error(SWT.java:4276)

!ENTRY org.eclipse.core.jobs 2 2 2016-01-08 12:56:41.840 !MESSAGE Job found still running after platform shutdown. Jobs should be canceled by the plugin that scheduled them during shutdown: com.ibm.cics.zos.ui.ZOSActivator$2