IIS6 App Pool issue

Hi,

I administer 3 seperate environments of IIS using the same code (different areas of development).  They are all hosted on 2003 SP2 servers and each environment cosists of a DC, SQL Server, 3x IIS Servers.  The App Pools are using a Domain Account which password does not expire.

Infrequently the errors occur in the environments which can stop the site.

Event Type:      Warning
Event Source:      W3SVC
Event Category:      None
Event ID:      1057
Date:            10/12/2008
Time:            13:41:00
User:            N/A
Computer:      Computer1
Description:
The identity of application pool 'AppPool' is invalid, so the World Wide Web Publishing Service can not create a worker process to serve the application pool.  Therefore, the application pool has been disabled.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.


Event Type:      Error
Event Source:      W3SVC
Event Category:      None
Event ID:      1059
Date:            10/12/2008
Time:            13:41:00
User:            N/A
Computer:      Computer1
Description:
A failure was encountered while launching the process serving application pool 'AppPool'. The application pool has been disabled.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.


Event Type:      Failure Audit
Event Source:      Security
Event Category:      Logon/Logoff
Event ID:      537
Date:            05/12/2008
Time:            05:04:45
User:            NT AUTHORITY\SYSTEM
Computer:      Computer1
Description:
Logon Failure:
       Reason:            An error occurred during logon
       User Name:      svcAccount
       Domain:            Domain
       Logon Type:      4
       Logon Process:      Advapi  
       Authentication Package:      Negotiate
       Workstation Name:      Computer1
       Status code:      0xC000005E
       Substatus code:      0x0
       Caller User Name:      Computer1$
       Caller Domain:      Domain
       Caller Logon ID:      (0x0,0x3E7)
       Caller Process ID:      1940
       Transited Services:      -
       Source Network Address:      -
       Source Port:      -


For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

I've done a fair bit of research in to this and it seems reasonably common and I've tried the following:
Reset Account Password on the DC & IIS - didn't fix the issue
Enabling the domain account in 'Act as Part of OS' - didn't fix the issue
Added Account to IIS_WPG user group - didn't fix the issue

I've read deleting the account and creating another may fix this but I've also been told this is just a bug in IIS6.

Are there any other suggestions on this issue or proof this is a bug as I've not found MS declaring this.

Thanks