posgres-7.1.3 hpux-11.00 posmaster died

Hello,

This morning I saw my database had no new record added since
yesterday.
And my db should be updated on the 15 min with hundreds of records !!

I tried first to connect to my db but I got the following answer:

>psql tkgdb1240
psql: connectDBStart() -- connect() failed: No such file or directory
        Is the postmaster running locally
        and accepting connections on Unix socket '/tmp/.s.PGSQL.5432'?

I wanted to restart postmaster with:

nohup /opt/postgres/bin/postmaster -i -D /db1240/data
1>>/home/postgres/server.log 2>&1 &

but I got this in my server.log:

Lock file "/db1240/data/postmaster.pid" already exists.
Is another postmaster (pid 6089) running in "/db1240/data"?

I displayed the process:

>ps -ef | grep post
postgres  6089     1  0  Dec 27  pts/ta    0:47
/opt/postgres/bin/postmaster -i -D /db1240/data
idxxxxxx 21087  3390  0 16:32:57 pts/ta    0:00 grep post
postgres 20590 20580  0 16:20:06 pts/tf    0:00 -ksh
idxxxxxx>

I started a top but saw nothing special. No hanging process.
No vacuum, no psql session, .... and 90 % of free resources.

What I see in my server.log is:

DEBUG:  copy: line 70, XLogWrite: new log file created - consider
increasing WAL
_FILES
DEBUG:  MoveOfflineLogs: remove 00000003000000BB

But I don't understand what it means :-(

Now I will kill the posmaster and start it again.
Any help greatly appreciated to understand what's happened.

Happy New Years from Belgium.
Pierre.