ERROR: scanNameSpaceForRefname: unexpected node type 0

Hello.
I have a 7.2 PostgreSQL Server working on a Debian and this afternoon during
a huge query I receive an unespected error message who terminate query
execution.
After this, every time I search to connect to whatever Database (e.g. with
psql) I receive this error message:

  ERROR:  scanNameSpaceForRefname: unexpected node type 0

Now, I have a backup of my data, but the problem persists dropping and
re-creating databases.
Can anybody suggest me how to do?
Shall I re-install PostgreSQL?

Thank you,
  Paolo Gibellini
  p.gibellini@teinos.com