DB2 connection causes "Unable to load one or more of the requested types. Retrieve the LoaderExce (4286168)

I'm getting the following error message when connecting to a DB2 database only.

System.Reflection.ReflectionTypeLoadException
Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.
Stack Trace:
at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
at System.Windows.Forms.Control.Invoke(Delegate method)
at Quest.Toad.Util.Facility.Load()
at Quest.Toad.Util.Facility.get_ImplementationType()
at Quest.Toad.DB2.DB2Provider.CreateProviderConnection(ConnectMediator mediator)
at Quest.Toad.Db.Provider.BackgroundConnector.CreateBackgroundConnection()

There are no other DB2 clients installed except TACOM11.