DCOM Security broken just like it was in XP SP2

When XP SP2 was released alot of applications broke as they did not have
permissions under DCOM (dcomcnfg)

Well lo and behold the application I am testing has broken again in Vista
(RC2) even though I think I have set the DCOM settings correctly.

Basically the application is calling a remote component I think
successfully, but it is doing so asyncronously so the component is required
to have security to call back to the client. So by adding security into
dcomcnfg for the service account that the component is running as under XP
SP2 allows it to call back, so why doesn't it in Vista?

I don't know!

Is there something else security wise I need to know about?

Thanks in advance