Can"t Edit Maintenance Plan

I have a clustered installation of SQL Server 2005 running on Windows
2003 with SSIS installed on the cluster.

I'm running SQL Server Management Server on one of the cluster nodes
and I can right click and create a new maintenance plan and drag a
'Back Up Database Task' into the plan. (Using the wizard also works.)

However if I try to open the the Backup item in the plan I get the
following error

===================================

Cannot show the editor for this task. (Microsoft SQL Server Management
Studio)

===================================

Exception from HRESULT: 0xC0010014
(Microsoft.SqlServer.DTSRuntimeWrap)

------------------------------
Program Location:

at
Microsoft.SqlServer.Dts.Runtime.ConnectionManager.get_Proper ties()
at
Microsoft.SqlServer.Management.DatabaseMaintenance.TaskConte xtUI.InitializeConnectionCombo(String
connectionName)
at
Microsoft.SqlServer.Management.DatabaseMaintenance.DBMaintTa skBackupForm.SetTask(DbMaintenanceBackupTask
task)
at
Microsoft.SqlServer.Management.DatabaseMaintenance.DBMaintTa skBackupForm..ctor(TaskHost
taskHost, IServiceProvider provider)
at
Microsoft.SqlServer.Management.DatabaseMaintenance.DbMaintTa skBackupUI.GetView()
at
Microsoft.DataTransformationServices.Design.DtrTaskDesigner. GetTaskEditor()

===================================

Exception from HRESULT: 0xC0010014
(Microsoft.SqlServer.DTSRuntimeWrap)

------------------------------
Program Location:

at
Microsoft.SqlServer.Dts.Runtime.Wrapper.IDTSPropertiesProvid er90.get_Properties()
at
Microsoft.SqlServer.Dts.Runtime.ConnectionManager.get_Proper ties()

I have searched and found various references to DTSRuntimeWrap,
including many unanswered queries and some which seem to refer to
making sure SSIS is set up on the cluster properly.

I passed on the information at http://msdn2.microsoft.com/en-us/library/ms345193(SQL.90).as px
to the installation engineer who tells me that all now been done and
that the servers are up to date with SP2.

Where can I go now? It seems a very specific error message but there
seems to be little information on a resolution.