There is a button called "Show Desktop" on the task bar.
When this is clicked, opened windows becomes icon. 
When clicked again, iconized windows show up again.
[windows]+[d] is assigned to this button as shot-cut key.

When a JavaSE licensee presses [windows]+[d] twice( whcih is, 
to iconize and restore windows), focus/caret in input field in java applicaitions 
disappears.

CONFIGURATION:
- OS : WindowsXP(SP2)/WindowsVista
- JDK : jdk5u18/jdk6u14

REPRODUCE:
1) Open "Notepad.jar" of Java Demo program
   (to invoke java -jar Notepad.jar)
2) input "abc'
   The caret is at the right of char. "c".
   You can see as follows.
 
    abc|

3) press [windows]+[d]  (Iconize)
4) press [windows]+[d]  (Restore)

5) There is no caret in the input field.

   abc

NOTE:
 1) This problem occurs in other Java aplicaitons. 
     ex. SwingSet2.jar
 2) The licensee tried the above reproduction procedure for
    notepad.exe in Windows. The caret is restored correctly.