LSASS error and server restart

I have a Windows 2003 Small Business Server that has just started to spontaneously restart. The event log shows application events similar to those described in MS artices 886174 and 818080.

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Article 886174:

Type: Error
Event ID: 1015
Source: Winlogon
Description: A critical system process, C:\WINDOWS\system32\lsass.exe, failed with status code c0000354. The machine must now be restarted.

Event Type: Error
Event Source: Application Error
Event Category: (100)
Event ID: 1000
Description: Faulting application lsass.exe, version 5.2.3790.0, faulting module authz.dll, version 5.2.3718.0, fault address 0x000023cc. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

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Article 818080:

Type: Error
Event ID: 1015
Source: Winlogon
Description: A critical system process, C:\WINDOWS\system32\lsass.exe, failed with status code c0000354. The machine must now be restarted.

Type: Error
Event ID: 1000
Source: Application Error
Description: Faulting application lsass.exe, version 5.2.3790.0, faulting module ntdsa.dll, version 5.2.3790.0, fault address 0x0008590f.
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With my server, EVENT ID 1015 is exactly as described. The key difference is that the 2nd Event ID 1000 error does not indicate the faulting module is either authz.dll or ntdsa.dll as each of these 2 articles would imply. The faulting module in EVENT ID 1000 in the 5 or so instances of my event log have been any of the following:

lsarv.dll
ntdll.dll
esent.dll


I have applied both hotfixes as well as a hotfix for article 875534 and it is still rebooting. Any suggestions would be appreciated.

Thanks,

Jerry