when I enter (code-char 256) in the repl, it dies, and in the minibuffer emacs says: Lisp connection died unexpectedly; exit code 256 (to that tune).
Using sbcl 0.9.8.0-1ubuntu3 and slime HEAD from cvs on Linux 2.6.15-27-686.
Do you have
(setq slime-net-coding-system 'utf-8-unix)
That's actually the key. The new sbcl uses the long char name, which consists only of safe letters.
When I made it return a string containing the A-with-macro, the connection died again.
Setting slime-net-coding-system yields the correct result, then.
I guess the packaged slimes look after what the host system uses for encoding and adapts, only I use cvs HEAD.
Error message would be nicer, though.
Thanks for figuring to everybody!
Florian