invalid multibyte character for locale

Hi,

I am testdriving postgresql 8.0.1.

On importing my old dump which works fine on 7.4.6 I am getting errors
like this one:

CREATE INDEX foobar_uvalue_key ON foobar USING btree (upper((value)::text));
ERROR: invalid multibyte character for locale
HINT: The server's LC_CTYPE locale is probably incompatible with the
database encoding.

pg_controldatas output (this is an EM64T machine (debian pure64), but
the issue also comes on 32bit Linux):

pg_control version number: 74
Catalog version number: 200411041
Database system identifier: 4763589314759867390
Database cluster state: in production
pg_control last modified: Wed Feb 23 22:07:43 2005
Current log file ID: 1
Next log file segment: 214
Latest checkpoint location: 1/D56163E8
Prior checkpoint location: 1/D56163A0
Latest checkpoint's REDO location: 1/D56163E8
Latest checkpoint's UNDO location: 0/0
Latest checkpoint's TimeLineID: 1
Latest checkpoint's NextXID: 3704
Latest checkpoint's NextOID: 50861184
Time of latest checkpoint: Wed Feb 23 21:40:25 2005
Database block size: 8192
Blocks per segment of large relation: 131072
Bytes per WAL segment: 16777216
Maximum length of identifiers: 64
Maximum number of function arguments: 32
Date/time type storage: floating-point numbers
Maximum length of locale name: 128
LC_COLLATE: C
LC_CTYPE: C

Should I be using de_DE or de_DE.UTF_8 locale? C locale always worked
fine for us (with 7.3 and 7.4).

Any hints?

Regards,
Bjoern