pcl erroring out for some unknown reason

[Darrell <shane%blackcomb@rand.org>]

At random places where I am defining methods and classes I will get 
an error message similar to the following:

Error: No matching method for the generic-function 
#<Function CLASS-PRECEDENCE-LIST @ #x5a3519>,
when called with arguments (NIL).

After the error, PCL is completely corrupt.  The error will be issued 
from then on whenever an instance is instantiated, including classes 
and methods.  Has anyone experienced this error before?  Any fixes, 
or guidance will be most appreciated.

Thanks,
Darrell Shane

P.S. I am running Victoria Day PCL on Allegro CL version 3.0.3.sun3.1