NLS_CHARACTERSET not being recognized?? help!

Hi listers,
Oracle 7.3.4, AIX 4.2.1

select * from NLS_DATABASE_PARAMETERS;

NLS_LANGUAGE                   AMERICAN                     =20
NLS_TERRITORY                  AMERICA                      =20
NLS_CURRENCY                   $                            =20
NLS_ISO_CURRENCY               AMERICA                      =20
NLS_NUMERIC_CHARACTERS         .,                           =20
NLS_DATE_FORMAT                'DD-MON-RR'                  =20
NLS_DATE_LANGUAGE              AMERICAN                     =20
NLS_CHARACTERSET               WE8ISO8859P1                 =20
NLS_SORT                       BINARY                       =20
NLS_CALENDAR                   GREGORIAN                    =20
NLS_RDBMS_VERSION              7.3.4.0.0=20

Database is updated via an application not builted in Oracle, and = suddenly
(not every day) data is not recognizing the nls_characterset:=20 the character "=F1" is being replaced by "?".

Any ideas of what should I check to solve this???

Thanks for any input on this topic,

Saludos,

Ver=F3nica Levin Enr=EDquez
Administrador AIX
Compa=F1=EDa Cervecera de Nicaragua
Tel=E9fono: 505-2493779
Fax: 505-2443979
Email: vlevin_at_victoria.com.ni=20 Received on Wed Jun 14 2000 - 14:35:29 CDT