I am using SBCL and Slime on windows.  When I make a mistake and Lisp goes to the debugger, the slime-repl often freezes Emacs. I will try to reproduce the error here:

; SLIME 2009-03-08
CL-USER> (* 3 4 5)
60
CL-USER> (reco 3 4) ;; I made a mistake on purpose

This error sends me to the debugger. When I abort (or try to return to Slime, or whatever), Emacs freezes:

; SLIME 2009-03-08
CL-USER> (* 3 4 5)
60
CL-USER> (reco 3 4) ;; I made a mistake on purpose

The minibuffer looks like this:

; pipelined request... (swank:listener-eval "3

The only thing that seems to work is Interrupt Lisp Process. BTW, here is the debugger loop:

The function RECO is undefined.
   [Condition of type UNDEFINED-FUNCTION]

Restarts:
 0: [RETRY] Retry SLIME REPL evaluation request.
 1: [ABORT] Return to SLIME's top level.
 2: [ABORT] Abort
 3: [CLOSE-CONNECTION] Close SLIME connection
 4: [ABORT] Exit debugger, returning to top level.

Backtrace:
  0: ("bogus stack frame")
  1: (SB-INT:SIMPLE-EVAL-IN-LEXENV (RECO 3 4) #<NULL-LEXENV>)
  2: (SWANK::EVAL-REGION "(reco 3 4) ;; I made a mistake on purpose\n")
  3: ((LAMBDA ()))
  4: (SWANK::TRACK-PACKAGE #<CLOSURE (LAMBDA #) {23F5029D}>)
  5: (SWANK::CALL-WITH-RETRY-RESTART "Retry SLIME REPL evaluation request." #<CLOSURE (LAMBDA #) {23F5022D}>)
  6: (SWANK::CALL-WITH-BUFFER-SYNTAX NIL #<CLOSURE (LAMBDA #) {23F50215}>)
  7: (SWANK::REPL-EVAL "(reco 3 4) ;; I made a mistake on purpose\n")
  8: (SB-INT:SIMPLE-EVAL-IN-LEXENV (SWANK:LISTENER-EVAL "(reco 3 4) ;; I made a mistake on purpose\n") #<NULL-LEXENV>)
  9: (SWANK::EVAL-FOR-EMACS (SWANK:LISTENER-EVAL "(reco 3 4) ;; I made a mistake on purpose\n") "COMMON-LISP-USER" 20)
 10: (SWANK::PROCESS-REQUESTS T)
 11: ((LAMBDA ()))
 12: (SWANK::HANDLE-REQUESTS #<SWANK::CONNECTION {241CC519}> T)
 13: ((LAMBDA (SWANK-BACKEND::HOOK SWANK-BACKEND::FUN)) #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> #<CLOSURE (LAMBDA #) {24236CED}>)
 14: (SWANK::CALL-WITH-BINDINGS NIL #<CLOSURE (LAMBDA #) {24236D05}>)
 15: (SWANK::CALL-WITH-CONNECTION #<SWANK::CONNECTION {241CC519}> #<CLOSURE (LAMBDA #) {24236CED}>)
 16: ((LAMBDA ()))
 17: ((LAMBDA ()))
 18: ((SB-PCL::FAST-METHOD STREAM-READ-CHAR (SWANK-BACKEND::SLIME-INPUT-STREAM)) #(2 NIL 3 NIL 1 NIL ...) #<unavailable argument> #<SWANK-BACKEND::SLIME-INPUT-STREAM {24235C91}>)
 19: (READ-CHAR #<SWANK-BACKEND::SLIME-INPUT-STREAM {24235C91}> T #:EOF-OBJECT #<unused argument>)
 20: (SB-IMPL::%READ-PRESERVING-WHITESPACE #<SWANK-BACKEND::SLIME-INPUT-STREAM {24235C91}> T NIL T)
 21: (SB-IMPL::%READ-PRESERVING-WHITESPACE #<SWANK-BACKEND::SLIME-INPUT-STREAM {24235C91}> T NIL NIL)
 22: (READ #<SWANK-BACKEND::SLIME-INPUT-STREAM {24235C91}> T NIL NIL)
 23: (SWANK::SIMPLE-REPL)
 24: ((LAMBDA ()))
 25: ((LAMBDA (SWANK-BACKEND::HANDLER FUNCTION)) #<FUNCTION (LAMBDA #) {23E05215}> #<CLOSURE (LAMBDA #) {241CC595}>)
 26: (SWANK::SIMPLE-SERVE-REQUESTS #<SWANK::CONNECTION {241CC519}>)
 27: (SWANK::SERVE-CONNECTION #<SB-BSD-SOCKETS:INET-SOCKET descriptor -1 {24158D89}> NIL NIL :ISO-8859-1)
 28: (SWANK::SETUP-SERVER 0 #<CLOSURE (LAMBDA #) {240E5FD5}> NIL NIL :ISO-8859-1)
 29: (SB-INT:SIMPLE-EVAL-IN-LEXENV (FUNCALL (READ-FROM-STRING "swank:start-server") "c:/DOCUME~1/User/CONFIG~1/Temp/slime.2900" :CODING-SYSTEM "iso-latin-1-unix") #<NULL-LEXENV>)
 30: (SB-INT:SIMPLE-EVAL-IN-LEXENV ..)
 31: (INTERACTIVE-EVAL ..)
 32: (SB-IMPL::REPL-FUN NIL)
 33: ((LAMBDA ()))
 34: (SB-IMPL::%WITH-REBOUND-IO-SYNTAX #<CLOSURE (LAMBDA #) {23B3910D}>)
 35: (SB-IMPL::TOPLEVEL-REPL NIL)
 36: (SB-IMPL::TOPLEVEL-INIT)
 37: ((LABELS SB-IMPL::RESTART-LISP))
 38: ("foreign function: #x412045")
 39: ("foreign function: #x40AEA8")