I'm using a byte-compiled slime.el.

Just FYI, here's your current compilation notes for emacs 23.1:

Compiling file /Users/ddp/.emacs.d/slime/slime.el at Tue Nov 3 09:50:45 2009 Entering directory `/Users/ddp/.emacs.d/slime/'

In slime-complete-maybe-restore-window-configuration: slime.el:3633:20:Warning: `last-command-char' is an obsolete variable (as of Emacs at least 19.34); use `last-command-event' instead.

In slime-next-line/not-add-newlines: slime.el:4698:10:Warning: `next-line' used from Lisp code That command is designed for interactive use only

In sldb-recenter-region: slime.el:5709:27:Warning: `next-line' used from Lisp code That command is designed for interactive use only

In slime-add-local-hook: slime.el:8555:11:Warning: `make-local-hook' is an obsolete function (as of Emacs 21.1); not necessary any more. Compiling no file at Tue Nov 3 09:50:59 2009