Drupal Colapsible fieldset dosn't works in edit mode

I figured out that the collapsed fieldset is not clickable if I try to edit in the not default language. I have two languages active. EN and NL. Everything works fine in EN (the standard language) while in NL I can't open the collapsed fieldset because the are not clickable.

Switch to standard language.

See: http://drupal.org/node/530614

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