IDE: trunk Build 200810010201
JDK: 1.6.0_05
OS: Windows XP, Solaris 10

to reproduce:
 - Run localized version (install ML, and run it in Japanese or Chinese locale)
 - Select main menu [Tools] > [Options]
 - Click [Edit] button in the displayed General panel
 - Modify any values in the displayed Web Browsers dialog, and click [OK]

The modification is discarded. It can be confirmed by re-opening Web Browsers dialog.

In my investigation, dialog works fine if the following message is translated back into English.

core.windows/src/org/netbeans/core/windows/services/Bundle.properties
   OK_OPTION_CAPTION=OK

I checked the source files a little and I'm guessing the following hardcoded "OK" causes this problem
(OK_OPTION_CAPTION=OK must not be translated). Line #335 in GeneralOptionsPanel.java

core.ui/src/org/netbeans/core/ui/options/general/GeneralOptionsPanel.java

330  private void editBrowserButtonActionPerformed(java.awt.event.ActionEvent evt) {
...
334              public void actionPerformed(ActionEvent e) {
335                  if( "OK".equals(e.getActionCommand()) ) {
336                      wbModel.applyChanges();
337                  } else {
338                      wbModel.discardChanges();
339                  }

The workaround is to translate OK_OPTION_CAPTION back into English, but the caption "OK" is back to English in other
customizer dialogs.