Issues with Upgrading PostgreSQL 8.4 to 9.0

I am trying to upgrade my PostgreSQL 8.4 (with PostGIS 1.5) to PostgreSQL 9.0 (with PostGIS 1.5) on Red Hat Linux 6.5, and have run into issues. I was going to try pg_dump method, but then I read about pg_upgrade. Here is the command I am running:

/usr/pgsql-9.0/bin/pg_upgrade -d /var/lib/pgsql/8.4/data/ -D /var/lib/pgsql/9.0/data/ -b /usr/pgsql-8.4/bin/ -B /usr/pgsql-9.0/bin/

But it results in the following error:

Performing Consistency Checks
-----------------------------
Checking old data directory (/var/lib/pgsql/8.4/data)       ok
Checking old bin directory (/usr/pgsql-8.4/bin)             ok
Checking new data directory (/var/lib/pgsql/9.0/data)       ok
Checking new bin directory (/usr/pgsql-9.0/bin)             ok
Checking for reg* system oid user data types                ok
Checking for /contrib/isn with bigint-passing mismatch      ok
Checking for large objects                                  ok
Creating catalog dump                                       /usr/pgsql-9.0/bin/pg_dumpall: symbol lookup error: /usr/pgsql-9.0/bin/pg_dumpall: undefined symbol: PQconnectdbParams


There were problems executing "/usr/pgsql-9.0/bin/pg_dumpall" --port 5432 --username "postgres" --schema-only --binary-upgrade -f "/var/lib/pgsql/pg_upgrade_dump_all.sql"

Any idea how I can resolve this issue? I may consider using pg_dump, but wanted to try the pg_upgrade method as advised by the official PostgreSQL documentation. I was also following instr I would like to upgrade my database to a more recent version of PostgreSQL, and read on StackOverflow that it is better to upgrade version by version so this is just the beginning I guess.

Thanks for your guidance.