unable to locate a valid checkpoint

Hi to all,

I'm quite new for this list, but I've already a big problem.
After a shutdown, the postmaster doesn't restart due to a checkpoint
error.
The data of the DB is ... ehm important... so, how can I recover my
installation?

message:
##########################################

FindExec: found "/usr/bin/postmaster" using argv[0]
2002-03-22 13:42:46 [6002]   DEBUG:  database system was shut down at
2002-03-22 11:46:11 CET
2002-03-22 13:42:46 [6002]   DEBUG:  ReadRecord: invalid resource manager
id 157 at (0, 561372168)
2002-03-22 13:42:46 [6002]   DEBUG:  Invalid primary checkPoint record
2002-03-22 13:42:46 [6002]   DEBUG:  Invalid RMID in secondary checkPoint
record
2002-03-22 13:42:46 [6002]   FATAL 2:  Unable to locate a valid CheckPoint
record
2002-03-22 13:42:46 [6002]   DEBUG:  proc_exit(2)
2002-03-22 13:42:46 [6002]   DEBUG:  shmem_exit(2)
2002-03-22 13:42:46 [6002]   DEBUG:  exit(2)
/usr/bin/postmaster: reaping dead processes...
/usr/bin/postmaster: Startup proc 6002 exited wit
##############################

TIA, Auri