Exchange 2010 setup: Error during /preparead

Hello all,

when trying to install 2010 in an existing Exchange 2003 environment, i get the following error:

Configuring Microsoft Exchange Server

    Organization Preparation         ......................... FAILED
     The following error was generated when "$error.Clear(); Install-AutoDiscove
rContainer -DomainController $RoleDomainController" was run: "Active Directory o
peration failed on MKDC01.intranet.test.name. This error is not retriable. A
dditional information: An attempt was made to modify an object to include an att
ribute that is not legal for its class.
Active directory response: 0000207D: UpdErr: DSID-031514DE, problem 6002 (OBJ_CL
ASS_VIOLATION), data -1735233997
".

The Exchange Setup log:

Ending processing.
[03.26.2010 12:17:56.0486] [1] Executing 'Install-AutoDiscoverContainer -DomainController $RoleDomainController' failed. The error is: False
[03.26.2010 12:17:56.0486] [2] Launching sub-task '$error.Clear(); Install-AutoDiscoverContainer -DomainController $RoleDomainController'.
[03.26.2010 12:17:56.0502] [2] Active Directory session settings for 'Install-AutoDiscoverContainer' are:  View Entire Forest: 'True', Configuration Domain Controller: 'MKDC01.intranet.test.name', Preferred Global Catalog: 'MKDC01.intranet.test.name', Preferred Domain Controllers: '{ MKDC01.intranet.test.name }'
[03.26.2010 12:17:56.0502] [2] Runspace context: Executing user: intranet.test.name/Intranet Users/Intranet Admins/Matthias Köhler, Executing user organization: , Current organization: , RBAC-enabled: Disabled.
[03.26.2010 12:17:56.0502] [2] Beginning processing.
[03.26.2010 12:17:56.0502] [2] Current ScopeSet is: {Domain Read Scope: {, }, Domain Write Scope(s): {, }, Configuration Scope: {, }, Server Configuration Scope(s): {, }, , Exclusive Scope: {, }}
[03.26.2010 12:17:56.0502] [2] Processing object "intranet.test.name/Configuration/Services/Microsoft Exchange Autodiscover".
[03.26.2010 12:17:56.0502] [2] Resolved current organization: .
[03.26.2010 12:17:56.0518] [2] The properties changed on the object '' (CN=Microsoft Exchange Autodiscover,CN=Services,CN=Configuration,DC=intranet,DC=test,DC=name) are: "{ Id[distinguishedName]='intranet.test.name/Configuration/Services/Microsoft Exchange Autodiscover', OrganizationId[msExchOURoot, msExchCU]='' }".
[03.26.2010 12:17:56.0533] [2] Saving object "intranet.test.name/Configuration/Services/Microsoft Exchange Autodiscover" of type "ADContainer" and state "New".
[03.26.2010 12:17:56.0611] [2] Previous operation run on domain controller 'MKDC01.intranet.test.name'.
[03.26.2010 12:17:56.0611] [2] [ERROR] Active Directory operation failed on MKDC01.intranet.test.name. This error is not retriable. Additional information: An attempt was made to modify an object to include an attribute that is not legal for its class.
Active directory response: 0000207D: UpdErr: DSID-031514DE, problem 6002 (OBJ_CLASS_VIOLATION), data -1735233997

[03.26.2010 12:17:56.0643] [2] [ERROR] An object class violation occurred.
[03.26.2010 12:17:56.0658] [2] Ending processing.
[03.26.2010 12:17:56.0658] [1] The following 1 error(s) occurred during task execution:
[03.26.2010 12:17:56.0658] [1] 0.  ErrorRecord: Active Directory operation failed on MKDC01.intranet.test.name. This error is not retriable. Additional information: An attempt was made to modify an object to include an attribute that is not legal for its class.
Active directory response: 0000207D: UpdErr: DSID-031514DE, problem 6002 (OBJ_CLASS_VIOLATION), data -1735233997

[03.26.2010 12:17:56.0658] [1] 0.  ErrorRecord: Microsoft.Exchange.Data.Directory.ADOperationException: Active Directory operation failed on MKDC01.intranet.test.name. This error is not retriable. Additional information: An attempt was made to modify an object to include an attribute that is not legal for its class.
Active directory response: 0000207D: UpdErr: DSID-031514DE, problem 6002 (OBJ_CLASS_VIOLATION), data -1735233997
 ---> System.DirectoryServices.Protocols.DirectoryOperationException: An object class violation occurred.
   at System.DirectoryServices.Protocols.LdapConnection.ConstructResponse(Int32 messageId, LdapOperation operation, ResultAll resultType, TimeSpan requestTimeOut, Boolean exceptionOnTimeOut)
   at System.DirectoryServices.Protocols.LdapConnection.SendRequest(DirectoryRequest request, TimeSpan requestTimeout)
   at Microsoft.Exchange.Data.Directory.PooledLdapConnection.SendRequest(DirectoryRequest request, LdapOperation ldapOperation, IAccountingObject budget)
   at Microsoft.Exchange.Data.Directory.ADSession.ExecuteModificationRequest(ADObject entry, DirectoryRequest request, ADObjectId originalId, Boolean emptyObjectSessionOnException)
   --- End of inner exception stack trace ---
   at Microsoft.Exchange.Data.Directory.ADSession.AnalyzeDirectoryError(PooledLdapConnection connection, DirectoryRequest request, DirectoryException de, Int32 totalRetries, Int32 retriesOnServer)
   at Microsoft.Exchange.Data.Directory.ADSession.ExecuteModificationRequest(ADObject entry, DirectoryRequest request, ADObjectId originalId, Boolean emptyObjectSessionOnException)
   at Microsoft.Exchange.Data.Directory.ADSession.Save(ADObject instanceToSave, IEnumerable`1 properties)
   at Microsoft.Exchange.Data.Directory.SystemConfiguration.ADSystemConfigurationSession.Microsoft.Exchange.Data.IConfigDataProvider.Save(IConfigurable instance)
   at Microsoft.Exchange.Configuration.Tasks.SetTaskBase`1.InternalProcessRecord()
   at Microsoft.Exchange.Configuration.Tasks.NewTaskBase`1.InternalProcessRecord()
   at Microsoft.Exchange.Configuration.Tasks.NewADTaskBase`1.InternalProcessRecord()
   at Microsoft.Exchange.Management.Tasks.InstallAutoDiscoverContainer.InternalProcessRecord()
   at Microsoft.Exchange.Configuration.Tasks.Task.ProcessRecord()
[03.26.2010 12:17:56.0674] [1] [ERROR] The following error was generated when "$error.Clear(); Install-AutoDiscoverContainer -DomainController $RoleDomainController" was run: "Active Directory operation failed on MKDC01.intranet.test.name. This error is not retriable. Additional information: An attempt was made to modify an object to include an attribute that is not legal for its class.
Active directory response: 0000207D: UpdErr: DSID-031514DE, problem 6002 (OBJ_CLASS_VIOLATION), data -1735233997
".
[03.26.2010 12:17:56.0674] [1] [ERROR] Active Directory operation failed on MKDC01.intranet.test.name. This error is not retriable. Additional information: An attempt was made to modify an object to include an attribute that is not legal for its class.
Active directory response: 0000207D: UpdErr: DSID-031514DE, problem 6002 (OBJ_CLASS_VIOLATION), data -1735233997

[03.26.2010 12:17:56.0674] [1] [ERROR] An object class violation occurred.

Any ideas which Objects are faulty and how to correct them?!

Cheers
Matthias