In the most recent alpha version of Allegro CL the arglist of the internal function INT-NEWEST-FRAME has changed slightly causing the slime debugger itself to signal an error. The backward compatible fix is:
--- swank-allegro.lisp.~1.142.~ 2011-02-18 12:06:00.000000000 +0100 +++ swank-allegro.lisp 2011-02-24 00:05:52.000000000 +0100 @@ -149,7 +149,7 @@ (defun find-topframe () (let ((magic-symbol (intern (symbol-name :swank-debugger-hook) (find-package :swank))) - (top-frame (excl::int-newest-frame))) + (top-frame (excl::int-newest-frame (excl::current-thread)))) (loop for frame = top-frame then (next-frame frame) for name = (debugger:frame-name frame) for i from 0
Cheers, Gabor