Postgres crashes

Can anyone help please. Intermittently a postgres/postmaster process appears to crash on our server and the postmaster service needs restarting. The following is entered in the log:

2006-03-15 09:50:03 LOG: server process (PID 348) was terminated by signal 125
2006-03-15 09:50:03 LOG: terminating any other active server processes
2006-03-15 09:50:06 FATAL: the database system is in recovery mode
2006-03-15 09:50:06 LOG: all server processes terminated; reinitializing
2006-03-15 09:50:06 FATAL: the database system is starting up
2006-03-15 09:50:06 LOG: database system was interrupted at 2006-03-15 00:16:39 GMT Standard Time
2006-03-15 09:50:06 LOG: checkpoint record is at 0/C1F3E48
2006-03-15 09:50:06 LOG: redo record is at 0/C1F3E48; undo record is at 0/0; shutdown FALSE
2006-03-15 09:50:06 LOG: next transaction ID: 651022; next OID: 113846
2006-03-15 09:50:06 LOG: database system was not properly shut down; automatic recovery in progress
2006-03-15 09:50:06 FATAL: the database system is starting up
2006-03-15 09:50:06 LOG: record with zero length at 0/C1F3E88
2006-03-15 09:50:06 LOG: redo is not required
2006-03-15 09:50:06 FATAL: the database system is starting up
2006-03-15 09:50:06 LOG: database system is ready

Alternatively I get the same messages as above but an additional WARNING regarding the crash of another server process has caused a rollback but it does not identify which process crashed.

When either occurs it is also accompanied by 2 postgres errors in the Application Log of the Win2K server:
(1) "the application failed to initialize properly (0xc0000142). Click on OK to terminate the application"
(2) "the exception unknown software exception (0xc00000fd) occurred in the application at 0x7c59bd01. Click on OK to terminate the application".

What is the signal 125 and how can I troubleshoot what is causing the process to crash as the error occurs at random times eg. 8pm when no-one is using the network and no utility is running such as AV or backup or during the day.

Thanks

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