Error while upgrading from 8.4 to 9.3

Hi, we are trying to upgrade from 8.4 to 9.3, but at the end of the
process we've got the error:

command: "/usr/lib/postgresql/9.3/bin/pg_resetxlog" -o 2429057 "/mnt/datos/datos_9.3/main" >> "pg_upgrade_utility.log"
2>&1
pg_resetxlog: lock file «postmaster.pid» exists
Is a server running?  If not, delete the lock file and try again.

Our setup is this:
Server: Ubuntu 12.04 – 32 bits
Clusters: Postgresql 8.4 y Postgresql 9.3

The steps we followed are:

1) pg_upgrade using –-check result Ok.
2) pg_upgrade without --check

Everything went ok, data directory was copied without problems.

At the end, we got the error I mentioned at the beggining of this email.

P.S.: pg_upgrade_utility.log attached.

Regards,
--
Leonardo M. Ramé
Medical IT - Griensu S.A.
Av. Colón 636 - Piso 8 Of. A
X5000EPT -- Córdoba
Tel.: +54(351)4246924 +54(351)4247788 +54(351)4247979 int. 19
Cel.: +54 9 (011) 40871877