error migrating database from 8.4 to 8.3

Due to a server issue we needed a reinstallation of Ubuntu along with a downgrade to Ubuntu Hardy.

So this is what we did:

- copied all from /var/lib/postgresql/8.4/main/ to the new server /var/lib/postgresql/8.3/main/
- edited /var/lib/postgresql/8.3/main/postmaster.opts to correct the path

Now trying to start the server results in

* Error: The server must be started under the locale : which does not exist any more.

I googled and found that people ran into this problem due to different architectures (32 vs 64 bit).
In this case, the architecture is definiately the same.

The only difference is that the database comes from a 8.4 installation and the server is 8.3

Please help solving this locale issue.

thanks!