Hi,
we had the same problem and were able to solve it.

The description of our solution might be a help to you as well:
We used the automation interface the following way: On a Windows 2003 server, we installed an EA build 830 completely and also a Java application that connects to a EA repository using the automation interface. This tiny java application is triggered by the windows scheduler every night to perform backup operations. Everything worked fine, until one certain day, when the automation interface threw a Unknown Exception (build 828) and with build 830 an exception with the following message: Failed to construct object. Error code: 0x80080005
We found out, that this error only happens, if no user is logged in into the server at the time the job is running (via remote desktop).
In this case, no complete Windows profile is available and hence there is a security problem. The solution is to define the correct user for the DCOM-Component execution:
In the control panel to go "Management" and choose "component services". There, expand component services folder until you can choose the DCOM Service folder. In there, you have to look for an entry named EA.APP. In the context menu choose "Properties" and go to the "identity" tab. Enter the username and password of the user with which the job should be executed.
Regards,
Tom