It seems that the string of "Ok" and "Cancel" for dialog buttons are hardcoded.
Please extract them to bundle file.
btnOk= new JButton( "Ok" );
btnCancel = new JButton( "Cancel" );
as it is I18N bug that influences ML release and Tasks are first class citizens now -> P2
Created attachment 71181 [details]
Integrated into 'main-golden', will be available in build *200810070201* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
User: S. Aubrecht <email@example.com>
Log: #149192 - I18N