Actually, the best troubleshooting tool I've come up with is to add a call to you base class that returns as much info as you can get on the object:

?oX.GetServerInfo()

Have it return stuff like _VFP.application and the clsid stored in a property.

_VFP application is a great help because it tells you the exact path to the .dll, from there you can use things like ADIR() to get more info.