FULL PRODUCT VERSION :
java version "1.5.0-rc"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-rc-b63)
Java HotSpot(TM) Client VM (build 1.5.0-rc-b63, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
Window.setLocationRelativeTo method is setting target window in center of referenced component. Unfortunately, it takes the total size of component, not only visible size - so for big component inside scroll pane, window is positioned at border of screen (instead in center of enclosing scroll pane).

This is most visible when using JOptionPane.showConfirmDialog when passing component being inside a scroll pane as a first parameter. As an addition problem, it cannot be even corrected by hand later, as call is modal.

This bug causes problems for generic actions, which are attached to multiple components and have to just use action source as context component for showing a confirmation dialog.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create a very big JTable, put it inside JScrollPane and show JOptionPane.showConfirmDialog(table...)

See attached source.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Confirmation dialog should appear in middle of visible table area
ACTUAL -
Confirmation dialog appears at bottom right edge of screen.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.*;
import javax.swing.*;

public class OptionTest {

  public static void main(String[] argv) {
    JFrame frame = new JFrame("Test");
    JTable table = new JTable();
    table.setPreferredSize(new Dimension(20000,20000));
    JScrollPane scrollpane = new JScrollPane(table);
    frame.setLayout(new BorderLayout());
    frame.add(scrollpane,BorderLayout.CENTER);
    frame.setSize(400,400);
    frame.setLocation(5,5);
    frame.setVisible(true);
    
    JOptionPane.showConfirmDialog(table, "Should be centered");
  }
  
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
In place where you call JOptionPane.showConfirmDialog, you can iterate component hierarchy up to see if there is a scrollpane there and in such case, pass it, instead of original component to showConfirmDialog.