Fixed in changeset:   173233:84ca576c42f5
http://hg.netbeans.org/main/rev/84ca576c42f5

Also the test demonstrates how can the event be used to make the cell conditionally editable based of the click location:
        @Override
        public boolean isCellEditable(EventObject anEvent) {
            if (anEvent.getSource() instanceof JTable) {
                JTable table = (JTable) anEvent.getSource();
                if (anEvent instanceof MouseEvent) {
                    MouseEvent event = (MouseEvent) anEvent;
                    Point p = event.getPoint();
                    int row = table.rowAtPoint(p);
                    int col = table.columnAtPoint(p);
                    Rectangle rect = table.getCellRect(row, col, true);
                    p.translate(-rect.x, -rect.y);
                    System.out.println("isCellEditable("+anEvent+")");
                    System.out.println("Point "+p+"in rectangle "+rect);
                    if (p.x > rect.width - 24) {
                        // last 24 points not editable
                        return false;
                    }
                }
            }
            return true;
        }

Integrated into 'main-golden', will be available in build *201006190001* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
Changeset: http://hg.netbeans.org/main/rev/84ca576c42f5
User: mentlicher@netbeans.org
Log: #187789 Call TableCellEditor.isCellEditable() and in the test we demonstrate how the cell can be made conditionally editable.

Please verify bugfix for this bug, so it can be integrated into release691 repository.

Thanks,
-R

Do not see any regression in 201006220001 - verified

I've prepared combined change in branch debugger_ports in release691 repository.

Integrated into release691 repository

changeset:   171826:8890faf51fd3
branch:      debugger_ports
parent:      171804:c30febb9fe6d
user:        mentlicher@netbeans.org
date:        Fri Jun 18 16:37:35 2010 +0200
summary:     #187789 Call TableCellEditor.isCellEditable() and in the test we demonstrate how the cell can be made conditionally editable.

verified in the source code