Hi Paolo,
I have just upgraded to CMUCL Snapshot 2005-10 (19C) and the latest SLIME CVS sources on my Linux box with GNU Emacs 21.3.2. Before trying SLIME with this new setup, I removed all fasl files from ~/.slime and the local SLIME sources in /home/paolo/src/slime.
When I issue `M-x slime' from Emacs, I get this error in the echo area, and SLIME doesn't start:
setq: Wrong type argument: listp, "cmucl -core /home/paolo/src/mcclim/clim.core"
[...]
(slime-register-lisp-implementation "clim" (format "cmucl -core %s" (expand-file-name "~/src/mcclim/clim.core")))
See http://article.gmane.org/gmane.lisp.slime.devel/4221 http://article.gmane.org/gmane.lisp.slime.devel/4223
HTH, Andras