Just for the heck of it, I installed SBCL from a package. Worked fine. But then I tried to use it in SLIME (latest version from CVS). No go.

* ;; Swank started at port: 32880.                                                                                              
                                                                                                                                
debugger invoked on a SIMPLE-ERROR in thread 3084629696:                                                                        
  There is no applicable method for the generic function                                                                        
    #<STANDARD-GENERIC-FUNCTION SWANK-BACKEND:SPAWN (0)>
  when called with arguments                                                                                                    
    (# :NAME "Swank").                                                                                                          
                                                                                                                                
Type HELP for debugger help, or (SB-EXT:QUIT) to exit from SBCL.                                                                
                                                                                                                                
restarts (invokable by number or by possibly-abbreviated name):                                                                 
  0: [ABORT] Exit debugger, returning to top level.                                                                             
                                                                                                                                
((SB-PCL::FAST-METHOD NO-APPLICABLE-METHOD (T))                                                                                 
 #<unavailable argument>
 #<unavailable argument>
 #<STANDARD-GENERIC-FUNCTION SWANK-BACKEND:SPAWN (0)>
 (#<CLOSURE # {958D2AD}> :NAME "Swank"))