Slime Version: 2.18 SBCL Version: 1.3.3 Having recently upgraded SBCL I pulled the latest quicklisp version of slime as well. I now get this error message popping up at random, but frequent intervals. It usually happens as I am typing at the REPL. I wonder if anyone might comment on what is happening - I can accept its my environment, but am at a loss as to how to track it down. Cheers The back trace is provided below: 0: ("bogus stack frame") 1: ("foreign function: maybe_now_maybe_later") 2: ("foreign function: _sigtramp") 3: ("foreign function: #x100B4A3F13") 4: (COMMON-LISP:FIND-SYMBOL "OR" #<COMMON-LISP:PACKAGE "SWANK-IO-PACKAGE">) 5: (SB-IMPL::OUTPUT-SYMBOL COMMON-LISP:OR #<SB-IMPL::STRING-OUTPUT-STREAM {100B4A6943}>) 6: ((COMMON-LISP:LABELS SB-IMPL::HANDLE-IT :IN SB-KERNEL:OUTPUT-OBJECT) #<SB-IMPL::STRING-OUTPUT-STREAM {100B4A6943}>) 7: (SB-IMPL::OUTPUT-LIST (COMMON-LISP:OR (:EMACS-REX . SWANK::_) (:EMACS-CHANNEL-SEND . SWANK::_)) #<SB-IMPL::STRING-OUTPUT-STREAM {100B4A6943}>) 8: ((COMMON-LISP:LABELS SB-IMPL::HANDLE-IT :IN SB-KERNEL:OUTPUT-OBJECT) #<SB-IMPL::STRING-OUTPUT-STREAM {100B4A6943}>) 9: (COMMON-LISP:PRIN1 (COMMON-LISP:OR (:EMACS-REX . SWANK::_) (:EMACS-CHANNEL-SEND . SWANK::_)) #<SB-IMPL::STRING-OUTPUT-STREAM {100B4A6943}>) 10: (SB-FORMAT::S-FORMAT-DIRECTIVE-INTERPRETER #<SB-IMPL::STRING-OUTPUT-STREAM {100B4A6943}> #<~s> (" " #<~s> #<~%>) #<unavailable argument> #<unavailable argument>) 11: (SB-FORMAT::INTERPRET-DIRECTIVE-LIST #<SB-IMPL::STRING-OUTPUT-STREAM {100B4A6943}> (#<~s> " " #<~s> #<~%>) ((COMMON-LISP:OR # #) T) ((COMMON-LISP:OR # #) T)) 12: (SB-FORMAT::%FORMAT #<SB-IMPL::STRING-OUTPUT-STREAM {100B4A6943}> "wait-for-event: ~s ~s~%" ((COMMON-LISP:OR # #) T) ((COMMON-LISP:OR # #) T)) 13: ((COMMON-LISP:LAMBDA NIL :IN SWANK::LOG-EVENT)) 14: (SB-IMPL::%WITH-STANDARD-IO-SYNTAX #<CLOSURE (COMMON-LISP:LAMBDA NIL :IN SWANK::LOG-EVENT) {100B4A680B}>) 15: (SWANK/SBCL::CALL-WITH-BREAK-HOOK #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> #<CLOSURE (LAMBDA NIL :IN SWANK::HANDLE-REQUESTS) {100B67322B}>) Locals: CONTINUATION = #<CLOSURE (LAMBDA () :IN SWANK::HANDLE-REQUESTS) {100B67322B}> HOOK = #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> 16: ((FLET SWANK/BACKEND:CALL-WITH-DEBUGGER-HOOK :IN "/Users/dbh/quicklisp/dists/quicklisp/software/slime-v2.18/swank/sbcl.lisp") #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> #<CLOSURE (LAMBDA NIL :IN SWANK::HAN.. 17: (SWANK::CALL-WITH-BINDINGS ((*STANDARD-INPUT* . #1=#<SWANK/GRAY::SLIME-INPUT-STREAM {100CFA82E3}>) (*STANDARD-OUTPUT* . #2=#<SWANK/GRAY::SLIME-OUTPUT-STREAM {100D07A0A3}>) (*TRACE-OUTPUT* . #2#) (*ERR.. 18: (SWANK::HANDLE-REQUESTS #<SWANK::SINGLETHREADED-CONNECTION {100C38F373}> T) 19: (SWANK::INVOKE-OR-QUEUE-INTERRUPT #<CLOSURE (LAMBDA NIL :IN SWANK::PROCESS-IO-INTERRUPT) {100B67292B}>) 20: (SWANK::PROCESS-IO-INTERRUPT #<SWANK::SINGLETHREADED-CONNECTION {100C38F373}>) 21: (SWANK/SBCL::SIGIO-HANDLER #<unused argument> #<unused argument> #<unused argument>) 22: ((FLET #:WITHOUT-INTERRUPTS-BODY-44 :IN SB-SYS:INVOKE-INTERRUPTION)) 23: ((FLET SB-THREAD::EXEC :IN SB-SYS:INVOKE-INTERRUPTION)) 24: ((FLET #:WITHOUT-INTERRUPTS-BODY-35 :IN SB-SYS:INVOKE-INTERRUPTION)) 25: (SB-SYS:INVOKE-INTERRUPTION #<CLOSURE (FLET SB-UNIX::INTERRUPTION :IN SB-SYS:ENABLE-INTERRUPT) {A1FEB5B}>) 26: ((FLET SB-UNIX::RUN-HANDLER :IN SB-SYS:ENABLE-INTERRUPT) 23 #.(SB-SYS:INT-SAP #X0A1FF168) #.(SB-SYS:INT-SAP #X0A1FF1D0))