slime breaking many emacs commands

[Brendan Miller]

In the slime repl, if I enter some invalid expression. Say, abc, I get 
this error in the minibuffer:

error in proces filter: Wrong type argument: characterp, nil

Then if I try to exit emacs (C-x C-c) I get this error:

Error in post-command-hook: (wong-type-argument characterp nil)

Thereafter C-x C-c and many other commands result in this error:

Wrong type argument: characterp, nil

So basically, when I use slime it ends up borking emacs, and forcing me 
to kill the process.

Has anyone seen this? Any tips for troubleshooting slime?

I'm using the slime install from quicklisp. I can upgrade to CVS, but I 
figure that the version in quicklisp is fairly widely used.

Thanks,
Brendan