LispWorks has a low args limit for apply. The following patch (inlined below) avoids landing on sldb when inspecting long lists. I think that its safe to #'nconc (nreverse ... but there isnt a noticeable change of speed or consing so it may be more conservative to just use reduce.
Index: swank.lisp =================================================================== RCS file: /project/slime/cvsroot/slime/swank.lisp,v retrieving revision 1.272 diff -u -r1.272 swank.lisp --- swank.lisp 16 Dec 2004 21:16:50 -0000 1.272 +++ swank.lisp 22 Dec 2004 21:56:41 -0000 @@ -2631,7 +2631,7 @@ (let ((a (if (null l) a (cons (label-value-line :tail l) a)))) - (apply #'append (reverse a))))))) + (reduce #'nconc (nreverse a))))))) (values title (append '("Elements:" (:newline)) lines)))))
(cond ((not length) ; circular