Are there any System Events happening on shutdown (Warnings or Errors)? The application events shouldn't really be causing this - they look like startup events anyways.
But to take care of your other Application Events - the warnings. Are you using the SNMP (Simple Network Management Protocol) service for anything? Normally, you shouldn't need it on a workstation (I've used it on Server 2003 systems), but I don't know if any of your software requires it, such as Unity. You could disable that service to get rid of the two warnings you are getting, or do a Registry edit. But I don't think that will take care of your shutdown problem either, but it's worth a shot to narrow down.
From MS KB832790:
To stop these events from occuring, add the TraceFileName and the TraceLevel values to the following registry subkey:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SNMP_EVENTS\EventLog\Parameters
TraceFileName
Type: REG_SZ
Value: null (blank)
TraceLevel
Type: REG_DWORD
Value: 32 (0x20)
http://support.microsoft.com/kb/832790
TC
