Undoing a presentation deftype ..

[buff%pravda@gatech.edu (Richard Billington)]

I accidentally left out the ":no-deftype t" incantation from
a presentation type I was defining - for which I have a flavor
of the same name. I was impatient when it was compiling and
told it to proceed even though it warned me it was going to
undefine this other (flavor-made) type. So, it's all my fault,
but it's really a pain because the type 'foo now is thought
to be a presentation type by the system, and I can't figure
out how to make it think otherwise - (typep <thing> 'foo) 
yields "don't do this with a presentation type" even though
I've since gone and recompiled the foo flavor definition,
etc.

For future reference (I'm going to reboot now - aarrrrrgh)
is there a way to undo or override this "damage"?