Automation Error?

I experienced the same problem recently with VB6 DCOM application. Please, read carefully the references below. At first glance I think that you need to recompile the client on the computer where the last version of the server was compiled. There is a reference to the server class and if there is no version match - the client can not create the remote object.
If this does not help, then try to reconfigure DCOM. Try the following:
1. Make sure you are using user level access control on the client (control panel\network)
2. If the user, logged on the client is not a domain user, then select: Default Authentication Level = None on the Server computer
3. If you have somebody logged on your server, then you can select: the interactive user in the Identity tab for your server application on the server machine. It is the least restrictive option. You may want to change it after you solve the problem.
4. You must have the same configuration options selected in the default tabs of dcomcnfg on the client machine, as the ones on the server. You may want to look at the server app options on the client machine. Read about finding the server key in client's Windows registry in the articles referenced below.
5. Not on the last place - if the server raises events and calls back to the client, then "Enable remote connection" should be checked in Default Security tab on the client machine.