Cannot start PostgreSQL

I have been workong with postgresql for months without problem and did not
change anything (I hope so). But now i cannot restart it. Starting with
pg_ctl start says 'postmaster successfully started', but when i try to check
with pg_ctl status it says 'pg_ctl: postmaster or postgres is not running'.
There is no matrching process to be seen with 'ps ax'. If i start postmaster
directly i see the following:

DBAdmin@linuxtest:~> postgres -D $PGDATA
LOG:  database system was shut down at 2004-09-07 11:15:03 CEST
LOG:  open of /home/DBAdmin/postgres/data/pg_xlog/000000010000003E (log file
1, segment 62) failed: Datei oder Verzeichnis nicht gefunden
LOG:  invalid primary checkpoint record
LOG:  open of /home/DBAdmin/postgres/data/pg_xlog/000000010000003E (log file
1, segment 62) failed: Datei oder Verzeichnis nicht gefunden
LOG:  invalid secondary checkpoint record
PANIC:  unable to locate a valid checkpoint record
Abgebrochen

'Datei oder Verzeichnis nicht gefunden' means in english: 'File or directory
not found'
'Abgebrochen' means in english 'Aborted'

The files noted in the above messages do not exist but there are otheres
called 0000000100000078 .. 000000010000007D

Has anyone an idea what might be the reason for this and how to recover.
Thanks in advance
----
R.Hnat