Can't update table rows!Probably encoding issue?

Hi!

Due to a server upgrade (new machine) i ran into the following problem, can anyone give me a hint?

Since porting the database on the new machine I can't update table columns containing a multi-line string (ie.
containinga line break). 

The old system was configured as follows:
Postgres 7.3.2 and system wide locale set to 'en_US'.
pg.catalog.pg_settings.server_encoding = SQL_ASCII
pg.catalog.pg_settings.client_encoding = SQL_ASCII
pg.catalog.pg_settings.lc_* = C

The new system is configured as follows:
Postgres 7.3.15 and system wide locale set to 'de_AT.UTF8'.
pg.catalog.pg_settings.client_encoding = SQL_ASCII
pg.catalog.pg_settings.client_encoding = SQL_ASCII
pg.catalog.pg_settings.lc_* = de_AT

The migration between the systems was done by generating a database dump using pg_dump on the old system and pgsql with
thedump on the new system. 

Cheers
Stefan