In your windows client look under:
HKEY_LOCAL_MACHINE>SOFTWARE>ORACLE
Key name: NLS_LANG
String: (Look in:
http://download-west.oracle.com/docs...a90236/toc.htm)
Other parameters that may be changed by the user session are the monetary paramaters that drive the currency and punctuation symbols: NLS_CURRENCY, NLS_ISO_CURRENCY, NLS_MONETARY_CHARACTERS which are driven by the 'TERRITORY' setting ing NLS_LANG or by default in NLS_TERRITORY.
You may want to check these settings in the database to compare against the setting of NLS_LANG in the clients.
Good luck.