What does "unclassable" mean?

[Francisco Miguel Colaço <fcolaco demnet ubi pt>]

I have caught this error in this particular object derived from GObject
when I instantiate it for the first time:

GLib-GObject-WARNING **: cannot unreference class of invalid (unclassed)
type `SsImage'

For the second time, it is even more intriguing:

GLib-GObject-CRITICAL **: file gobject.c: line 615 (g_object_new):
assertion `G_TYPE_IS_OBJECT (object_type)' failed

I have used the same skeleton over and over again without a problem to
date to derive GObject, and I have double checked (and even done it
again from scratch).  However, the problem seems to persist.

What is this?  Where is my error?  What should I do to correct or, at
the very least, get around it?

    Francisco


-- 
Francisco Miguel Colaço <fcolaco demnet ubi pt>
Universidade da Beira Interior