the problem of createlang!

I have installed postgresql (version 7.4.5) on the Redhat linux
platform.

Now I want to create a database with name BBMF and create pl/pgsql
procedure language to the BBMF

The problem is listed follow:

[postgres(at)wap1-np postgresql-7.4.5]$ psql -l

List of databases

Database | Owner | Encoding

-----------+----------+-----------

BBMF | develop | SQL_ASCII

template0 | postgres | SQL_ASCII

template1 | postgres | SQL_ASCII

(3 rows)

[postgres(at)wap1-np postgresql-7.4.5]$ createlang plpgsql BBMF

ERROR: Load of file /usr/local/pgsql/lib/plpgsql.so failed:
/usr/local/pgsql/lib/plpgsql.so: undefined symbol: error_context_stack

createlang: language installation failed

[postgres(at)wap1-np postgresql-7.4.5]$ file
/usr/local/pgsql/lib/plpgsql.so

/usr/local/pgsql/lib/plpgsql.so: ELF 32-bit LSB shared object, Intel
80386, version 1, not stripped

[postgres(at)wap1-np postgresql-7.4.5]$

What's the matter ?

Please help me!!!