I have trouble installing postgresql with apt.

postgresql-9.1 (or postgresql-9.3) installation fails with:

* Starting PostgreSQL 9.1 database server

* Error: could not exec /usr/lib/postgresql/9.1/bin/pg_ctl /usr/lib/postgresql/9.1/bin/pg_ctl start -D /var/lib/postgresql/9.1/main -l  /var/log/postgresql/postgresql-9.1-main.log -s -o  -c  config_file="/etc/postgresql/9.1/main/postgresql.conf" :

                                                                                                                                                                                                                               [fail]

invoke-rc.d: initscript postgresql, action "start" failed.

When I try executing /usr/lib/postgresql/9.1/bin/pg_ctl /usr/lib/postgresql/9.1/bin/pg_ctl start -D /var/lib/postgresql/9.1/main -l /var/log/postgresql/postgresql-9.1-main.log -s -o -c config_file="/etc/postgresql/9.1/main/postgresql.conf"directly, it fails with:

/usr/lib/postgresql/9.1/bin/pg_ctl: symbol lookup error: /usr/lib/postgresql/9.1/bin/pg_ctl: undefined symbol: PQping

Here is my system information:

$ uname -a

Linux daclin 3.2.0-23-generic #36-Ubuntu SMP Tue Apr 10 20:39:51 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

Would you have any idea on what is going on?