Exchange store.exe crashes every night at approx 04.02

Hi
We have an exchange server which requires a reboot every morning.
At 0402 each night the following events are logged:
--------------------------------
Event Type:      Information
Event Source:      ESE
Event Category:      Logging/Recovery
Event ID:      210
Date:            12/08/2008
Time:            04:02:05
User:            N/A
Computer:      FMC2K301
Description:
Information Store (7804) First Storage Group: A full backup is starting.
--------------------------------
Event Type:      Information
Event Source:      ESE
Event Category:      Logging/Recovery
Event ID:      220
Date:            12/08/2008
Time:            04:02:05
User:            N/A
Computer:      FMC2K301
Description:
Information Store (7804) First Storage Group: Beginning the backup of the file C:\Program Files\Exchsrvr\mdbdata\priv1.edb (size 4856 Mb).
--------------------------------
Event Type:      Information
Event Source:      ESE BACKUP
Event Category:      Backup
Event ID:      909
Date:            12/08/2008
Time:            04:02:26
User:            N/A
Computer:      FMC2K301
Description:
Information Store (7804) Backup data transfer method is RPC.
--------------------------------

Then very soon after, and the time does differ, we get the following errors
Event Type:      Error
Event Source:      Microsoft Exchange Server
Event Category:      None
Event ID:      1000
Date:            12/08/2008
Time:            04:02:33
User:            N/A
Computer:      FMC2K301
Description:
Faulting application store.exe, version 6.5.7638.2, stamp 434353c1, faulting module ese.dll, version 6.5.7638.2, stamp 43433bbb, debug? 0, fault address 0x00046f0a.

I have ensured all backups are not running to test and we still get the error.

Can anyone please shed some light on why the ESE event is logging when no backups run?

Thanks