Thread Subject: Error starting desktop (plizz...help me)

help me...
i have a problem..
when i open MATLAB 71, I get an error message saying the
following:

Error Starting Desktop
com.mathworks.mwswing.desk.DTNestingContainer$TreeState.find
SubTree(DTNestingContainer.java:1840)
com.mathworks.mwswing.desk.DTNestingContainer.getPreviousLoc
ation(DTNestingContainer.java:765)
com.mathworks.mwswing.desk.DTNestingContainer.add
(DTNestingContainer.java:135)
com.mathworks.mwswing.desk.DTMultipleClientFrame.addClient
(DTMultipleClientFrame.java:298)
com.mathworks.mwswing.desk.Desktop.setClientShowing
(Desktop.java:3856)
com.mathworks.mwswing.desk.Desktop.setClientShowing
(Desktop.java:3672)
com.mathworks.mwswing.desk.Desktop.showClientWithoutActivati
ngFrame(Desktop.java:3943)
com.mathworks.mde.desk.MLDesktop.access$300
(MLDesktop.java:42)
com.mathworks.mde.desk.MLDesktop$2.run(MLDesktop.java:329)
java.awt.event.InvocationEvent.dispatch(Unknown Source)
java.awt.EventQueue.dispatchEvent(Unknown SOurce)
java.awt.EventDispatchThread.pumpOneEventForHierarchy
(Unknown Source)
java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown
Source)
java.awt.EventDispatchThread.pumpEvents(Unknown Source)
java.awt.EventDispatchThread.pumpEvents(Unknown Source)
java.awt.EventDispatchThread.run(Unknown Source)

its began when i closed workspace, history, and current
directory one by one from File menu (not Exit directly).
i don't know how to repair that...
help me, plizzz...
b'coz i need it to finishing my final project...