OWB 11.03 o, Solaris:
BASE_LANGUAGE 'Dutch_Netherlands' SUPPORTED_LANGUAGES 'English_United';
does not accept the languages settings, default languages settings are used for seeding ythe dictionatry!
I assume that the OWBSYS user is new and you are seeding it for the first time if not you can not change the base language once seeded.
for base language try using DUTCH (instaed of Dutch_Netherlands because i can see there is one otpion for dutch language which is DUTCH).