ESA 3.0 error when accessing shared mailboxes

Platform: ESA3 installed on W2003/Exchange 2003 standard server

When attempting to access a shared mailbox (an individual mailbox with mailbox rights extended to specified AD users) the user sees the following message:

User DOMAIN\UserName group cannot be granted permission on the mailbox membership@theidm.com - no archive service which could be contacted allowed this.

Archiving solution working perfectly for standard individual accounts.

The 2 errors recorded in the log files are:
Message 1:
CheckPermissions
Archive Service could not verify permissions for user: THEIDM\membership_group. Ensure this is not a local account.
RedGate.ExchangeArchiver.ArchiveService.Interface.ArchiveServiceException: Cannot check permissions on mailbox '1a62fc0b-7f98-49d5-9b6a-b855e7997a73' for user 'THEIDM\membership_group'.
Ensure the Archive Service is running as a domain user with the required permissions. For more details, see http://www.red-gate.com/ESA/3.0?i=9420 .

Server stack trace:
at RedGate.ExchangeArchiver.ArchiveService.Engine.ArchiveService.CheckUserPermissionOnMailbox(Guid mailboxGuid, String netbiosUsername)
at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Int32 methodPtr, Boolean fExecuteInContext, Object[]& outArgs)
at System.Runtime.Remoting.Messaging.StackBuilderSink.PrivateProcessMessage(RuntimeMethodHandle md, Object[] args, Object server, Int32 methodPtr, Boolean fExecuteInContext, Object[]& outArgs)
at System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage msg, Int32 methodPtr, Boolean fExecuteInContext)

Exception rethrown at [0]:
at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
at RedGate.ExchangeArchiver.ArchiveService.Interface.IArchiveService.CheckUserPermissionOnMailbox(Guid mailboxGuid, String netbiosUsername)
at RedGate.ExchangeArchiver.UserArchiveAccessService.Engine.Engine.UAAEngine.a(String , Guid )

Message 2:
Job Controller
RedGate.ExchangeArchiver.Exchange.Interface.ExchangeAbstractionException: Cannot check permissions on mailbox '1a62fc0b-7f98-49d5-9b6a-b855e7997a73' for user 'THEIDM\membership_group'.
Ensure the Archive Service is running as a domain user with the required permissions. For more details, see http://www.red-gate.com/ESA/3.0?i=9420 . ---> System.MissingMethodException: Method not found: 'Boolean System.Threading.WaitHandle.WaitOne(Int32)'.
at k.a(b )
at p.b(String )
at p.d(String )
at l.<>c__DisplayClass3.<CheckUserPermissionOnMailbox>b__0()
at l.a(b , a , a )
--- End of inner exception stack trace ---
at l.<>c__DisplayClass3.<CheckUserPermissionOnMailbox>b__2(Exception ex)
at l.a(b , a , a )
at l.a(Guid , String )
at RedGate.ExchangeArchiver.ActiveDirectory.ActiveDirectoryService.CheckUserPermissionOnMailbox(Guid mailboxGuid, String netbiosUsername)
at RedGate.ExchangeArchiver.ArchiveService.Engine.ArchiveService.CheckUserPermissionOnMailbox(Guid mailboxGuid, String netbiosUsername)
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