This sort of question usual complains about improper display of text coming from a database rather than from a SQL script. Anyway...
1. Check your NLS settings: Tools > Preferences > Database > NLS
2. Note that 3.0.03 was an Early Adopter release, not a production release. See 3.0.04.34, or patch release 3.0.04.61, or even the latest 22.214.171.124.21
If I've misunderstood the question and the text does come from the database, perhaps the follow discussions will help you:
SQL Developer Team