PG_exception_stack

Hello,

When I run:
createlang plpgsql wetter

i get the error:
ERROR:  could not load library "/usr/local/pgsql/lib/plpgsql.so":
/usr/local/pgsql/lib/plpgsql.so: undefined symbol: PG_exception_stack

I found something in the net:

"I think you've got a version mismatch problem --- specifically, it looks
like you are trying to load an 8.0 plpgsql.so into a pre-8.0 backend.
PG_exception_stack is (just by chance no doubt) the first symbol the
newer code tries to reference that's not in the older backend."

I'm running PostgreSQL 8.0.3 und Suse 9.2.
Can anybody tell me whats wrong.

Thanks a lot!

Greetings
Maik