database "postgres" does not exist

Hello everybody

We have a very strange problem here: we have been using postgresql for
several years now, it runs fine without any problem.
BUT today, we saw something I do not understand:

when I try to use psql like this:
sudo -u postgres psql
I get the message:
psql: FATAL: database "postgres" does not exist

About 1-2 months ago, this was OK

I know this message is current on a new installation when the system is
NOT initialized.
But what puzzles me here is that the database postgres DID exist... but
it seems to have suddenly disappeared !!!!

A part from this, everything works fine, for example the command:
sudo -u postgres psql -d template1
works, and the postgres applications run quite smoothly

So, here is my question: how such a thing could have happen ? We cannot
remeber any stupid thing we could have done (but may be we did... And
what do I have to do to recreate the postgres database... in fact, is it
even necessary doing so ?

The OS is a 64bits Debian (distribution testing, dist-upgraded today but
this did not correct the problem)
The postgres version is 8.1.4

Thanks in advance,

--
Emmanuel COURCELLE emmanuel(dot)courcelle(at)toulouse(dot)inra(dot)fr
L.I.P.M. (UMR CNRS-INRA 2594/441) tel (33) 5-61-28-54-50
B.P.52627 - 31326 CASTANET TOLOSAN Cedex - FRANCE
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