Debugging asp.net component

[Andy]

I have a component I'm trying to debug when used in the design time
environment. When the designer opens, the control gives an exception
and this is dislplayed:

There was an error rendering the control.
Exception has been thrown by the target of an invocation.

So I know I'm trying to track down a TargetInvocationException, but I
don't know where to begin looking. Anyway I can get more detail?

Andy