Unable to delete a SQL 2005 Maintenance Plan

When trying to delete a SQL 2005 Maintenance Plan through the Object Explorer, I receive the following error:

Microsoft SQL Server Management Studio

  Exception has been thrown by the target of invocation. (mscrolib)

  Additional Information:

       There is no row at position 0. (System.Data)

Here is the info under Advanced Information about the error:

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Exception has been thrown by the target of an invocation. (mscorlib)

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Program Location:

   at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
   at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.SqlServer.Management.SqlManagerUI.DropMaintPlans.DoDropMaintPlan90(String planID, String planName)
   at Microsoft.SqlServer.Management.SqlManagerUI.DropMaintPlans.DoDropObject(Int32 objectRowIndex)
   at Microsoft.SqlServer.Management.SqlManagerUI.DropObjects.DropAllObjects(Boolean stopOnError)

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

There is no row at position 0. (System.Data)

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Program Location:

   at System.Data.RBTree`1.GetNodeByIndex(Int32 userIndex)
   at System.Data.RBTree`1.get_Item(Int32 index)
   at System.Data.DataRowCollection.get_Item(Int32 index)
   at Microsoft.SqlServer.Management.DatabaseMaintenance.MaintenancePlanSubPlan.GetSubPlanJob(ServerConnection userConnection)
   at Microsoft.SqlServer.Management.DatabaseMaintenance.MaintenancePlan.InitFromExistingPackage(Package package, ServerConnection localConnObj)
   at Microsoft.SqlServer.Management.DatabaseMaintenance.MaintenancePlan..ctor(Package package, String serverName, String userName, SqlSecureString pwd)
   at Microsoft.SqlServer.Management.DatabaseMaintenance.MaintenancePlan.GetMaintenancePlanFromServer(String maintPlanName, String serverName, String userName, SqlSecureString pwd)

I have more than one plan that gets this error.

Any ideas how they can be deleted?

Thanks,
Jeff