jdk 7u25 b09, de

Steps to reproduce:
1. Run SwingSet2
2. Change Look&Feel to "GTK Style Look & Feel"
3. Go to JFileChooser demo
4. Click on "Show Plain JFileChooser" or "Show Preview JFileChooser" button

The dialog box that pops up contains mnemonic placed on the same letter ("O").
Please refer to the attached screen shot.