Help with COM+ LCE subscriber problem for own event class

[Graeme Chambers]

I have created my own event class, publisher, and subscribers in
C# .NET The event class and subscriber definitions exist in the same
library. The publisher is a stand alone app which references this
library. The subscriber is a windows service which also references
this library.

In the windows service subscriber, I am able to receive normal COM+
events such as AppActivation, ActivityEvents, etc etc, but I am having
trouble receiving events from my own event class.

I am getting the event log error: The COM+ Event System failed to fire
the XXXX method on subscription {C453C1FB-FEC1-45BB-ACBF-F8C923D9D616}-
{41E90F3E-56C1-4633-81C3-6E8BAC8BDD70}-
{00000000-0000-0000-0000-000000000000}. The subscriber returned
HRESULT 80070005.

My subscription code is:
ICatalogObject subscription = (ICatalogObject)transients.Add();
subscription.set_Value("Name", this.ToString()); // name it
subscription.set_Value("EventCLSID", GetEventClassID());
subscription.set_Value("InterfaceID", GetEventInterfaceID());
subscription.set_Value("SubscriberInterface", GetIUnknown());
bool success = transients.SaveChanges() == 0;

Can anybody help me out here, please? I've searched for that HRESULT
but can't find any meaningful responses for my situation.

Thanks