Getting 0x80131902 when calling COM+ component

Update: Even if I remove the Application Root Directory it gives the same error - the only way I can get it to run is in a library process, not a server process.

Original question: I created a COM+ component in .Net. It needs to use a configuration file, so I've created a directory with an application.manifest and application.config file and set that as the Application Root Directory. Now when I try to create an instance of that object, I get the following HRESULT: 0x80131902. I can't seem to find exactly what this means, except that there is a problem loading the app-domain. If I don't set the Application Root Directory, it loads just fine (but doesn't have access to the config).

Turns out that was because I was throwing an exception during the constructor of the COM+ component. Hopefully this will help someone out in the future.