Possibly corrupted shared memory, PostgreSQL 8.1 beta2, Windows 2000

Hi,

I've installed PostgreSQL 8.1 beta2 five days ago and it crashed 3 times
since then.
Here is what's been logged for the last crash

2005-10-04 11:00:19 FATAL: could not read block 121 of relation
1663/16384/2608: Invalid argument
2005-10-04 11:00:20 LOG: server process (PID 2592) was terminated by signal
1
2005-10-04 11:00:20 LOG: terminating any other active server processes

Than for each connections, the log has:
2005-10-04 11:00:20 WARNING: terminating connection because of crash of
another server process
2005-10-04 11:00:20 DETAIL: The postmaster has commanded this server
process to roll back the current transaction and exit, because another
server process exited abnormally and possibly corrupted shared memory.
2005-10-04 11:00:20 HINT: In a moment you should be able to reconnect to
the database and repeat your command.

With this in the end:
2005-10-04 11:00:20 LOG: all server processes terminated; reinitializing
2005-10-04 11:00:21 LOG: database system was interrupted at 2005-10-04
10:59:43 Eastern Daylight Time

relation 2608 is pg_depend
----------------------------------------------------------------------------------
The crash before that was on relation pg_type, the first line logged was:
2005-10-03 10:51:06 FATAL: could not read block 38 of relation
1663/16384/1247: Invalid argument
----------------------------------------------------------------------------------
The first crash was also on relation pg_depend, but with open instead or
read
2005-09-30 18:38:53 FATAL: could not open relation 1663/16384/2608: Invalid
argument
----------------------------------------------------------------------------------

There was between 14 and 17 connections when these crashes happened.

The database was not reloaded from a backup but created from
.sql scripts for DDL, and data from user tables were reloaded
from files with "copy from".

We are using Windows 2000 Server, Service Pack 4.

Thanks,
Jean-Pierre Pelletier
e-djuster