print-unreadable-object recursion

This is not a bug. If you don't bind a slot, it's normal to get an error when you try to access it.
Either don't try to read unbound slot, or bind all your slots (with :initform).

[pjb@kuiper :0 ~]$ clisp -ansi -norc -q
[1]> (defclass c1 ()
((name :initarg :name :accessor name-of)))
#<STANDARD-CLASS C1>
[2]> (defmethod print-object ((c c1) stream)
(print-unreadable-object (c stream :type t :identity t)
(princ (name-of c) stream)))
#<STANDARD-METHOD (#<STANDARD-CLASS C1> #<BUILT-IN-CLASS T>)>
[3]> (make-instance 'c1 :name "Hello")
#<C1 Hello #x000333D0E7A0>
[4]> (defmethod print-object ((c c1) stream)
(print-unreadable-object (c stream :type t :identity t)
(when (slot-boundp c 'name) (princ (name-of c) stream))))
WARNING: Replacing method
#<STANDARD-METHOD (#<STANDARD-CLASS C1> #<BUILT-IN-CLASS T>)> in
#<STANDARD-GENERIC-FUNCTION PRINT-OBJECT>
#<STANDARD-METHOD (#<STANDARD-CLASS C1> #<BUILT-IN-CLASS T>)>
[5]> (make-instance 'c1)
#<C1 #x000333D29580>
[6]> (quit)
[pjb@kuiper :0 ~]$

This is not a bug. When writing a PRINT-OBJECT method you have to be more careful
and more defensive than elsewhere, precisely because PRINT-OBJECT can be used in
error messages.

Change your method like this:
(defmethod print-object ((c c1) stream)
(print-unreadable-object (c stream :type t :identity t)
(when (slot-boundp c 'name) (princ (name-of c) stream))))