New problems in SBCL 1.0

I'm trying the CVS version of CLG in SBCL 1.0, but a can't compile gtk
system, when compiling the file gtktype.lisp I get this error:

illegal to redefine standard type NIL

But, If I retry the compilation I get this error:

While computing the class precedence list of the class named
PRINT-BACKEND-MODULE.
It is not possible to compute the class precedence list because
there is a circularity in the local precedence relations.
This arises because:
  The class #<FORWARD-REFERENCED-CLASS NIL> follows the class
#<FORWARD-REFERENCED-CLASS NIL> in the supers of the class named
PRINT-BACKEND-MODULE..


-- 
"Lisp isn't a language, it's a building material." - Alan Kay

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