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