This one was nasty -- it crashed repeatedly until I did pkill kpdf at a tty.

Asynchronous ATOM-ERROR in request 2582 (last request was 2583)  Code 17.0 Atom-ID #x45B73B
<1/148> #<SYSTEM-FUNCTION SHOW-STACK> 3
<2/144> #<COMPILED-FUNCTION STUMPWM::PRINT-BACKTRACE>
[143] unwind-protect frame
- #<COMPILED-FUNCTION STUMPWM::BACKTRACE-STRING>
<3/137> #<COMPILED-FUNCTION STUMPWM::BACKTRACE-STRING>
- :TOP-LEVEL
- #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP-1-1>
<4/133> #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP-1-1>
- #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP-1-1>
- #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP>
<5/129> #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP>
- #<XLIB:ATOM-ERROR #x0003345BF670>
<6/124> #<SYSTEM-FUNCTION SIGNAL> 1
[123] frame binding variables (~ = dynamically):
  | ~ SYSTEM::*CONDITION-RESTARTS* <--> NIL
[117] compiled tagbody frame for #(NIL)
- 
#(#(NIL "Ignore"
    (:DISPLAY #<XLIB:DISPLAY localhost:0 (The X.Org Foundation R10400090) X11.0 #x000334527D48> :ERROR-KEY XLIB:ATOM-ERROR :ASYNCHRONOUS T
     :CURRENT-SEQUENCE 2583 :SEQUENCE 2582 :MAJOR 17 :MINOR 0 :ATOM-ID 4568891))
  NIL)
- 
#(NIL "Ignore"
  (:DISPLAY #<XLIB:DISPLAY localhost:0 (The X.Org Foundation R10400090) X11.0 #x000334527D48> :ERROR-KEY XLIB:ATOM-ERROR :ASYNCHRONOUS T :CURRENT-SEQUENCE
   2583 :SEQUENCE 2582 :MAJOR 17 :MINOR 0 :ATOM-ID 4568891))
- 
(:DISPLAY #<XLIB:DISPLAY localhost:0 (The X.Org Foundation R10400090) X11.0 #x000334527D48> :ERROR-KEY XLIB:ATOM-ERROR :ASYNCHRONOUS T :CURRENT-SEQUENCE
 2583 :SEQUENCE 2582 :MAJOR 17 :MINOR 0 :ATOM-ID 4568891)
- "Ignore"
<7/109> #<COMPILED-FUNCTION CERROR>
- #<COMPILED-FUNCTION STUMPWM::ERROR-HANDLER>
- (:ASYNCHRONOUS T :CURRENT-SEQUENCE 2583 :SEQUENCE 2582 :MAJOR 17 :MINOR 0 :ATOM-ID 4568891)
- #<XLIB:DISPLAY localhost:0 (The X.Org Foundation R10400090) X11.0 #x000334527D48>
<8/104> #<COMPILED-FUNCTION STUMPWM::ERROR-HANDLER>
<9/114> #<SYSTEM-FUNCTION FUNCALL> 15
- #<XLIB:DISPLAY localhost:0 (The X.Org Foundation R10400090) X11.0 #x000334527D48>
<10/100> #<ADD-ON-SYSTEM-FUNCTION XLIB:ATOM-NAME> 2
- (4568891)
- :_NET_WM_STATE
<11/95> #<COMPILED-FUNCTION STUMPWM::UPDATE-WINDOW-PROPERTIES>
- #S(window "Erann Gat - Idiots Guide To Lisp Packages.pdf - KPDF" #x2000006)
- :NEW-VALUE
- #<XLIB:WINDOW 1278x798+0+0 localhost #x02000006 #x000334589D58>
<12/91> #<COMPILED-FUNCTION #:G39577>
- #<COMPILED-FUNCTION #:G39577>
[83] catch frame for tag #:SIMPLE-RESTART-40057
<13/79> #<COMPILED-FUNCTION STUMPWM::HANDLE-EVENT-2>
- #<COMPILED-FUNCTION STUMPWM::HANDLE-EVENT-2>
- #<COMPILED-FUNCTION STUMPWM::HANDLE-EVENT-2>
[72] compiled tagbody frame for #(NIL)
- 
#(#(#(NIL
      (:DISPLAY #<XLIB:DISPLAY localhost:0 (The X.Org Foundation R10400090) X11.0 #x000334527D48> :EVENT-CODE 28 :SEND-EVENT-P NIL :SEQUENCE 2027
       :EVENT-KEY :PROPERTY-NOTIFY :WINDOW #<XLIB:WINDOW 1278x798+0+0 localhost #x02000006 #x000334589D58> :EVENT-WINDOW
       #<XLIB:WINDOW 1278x798+0+0 localhost #x02000006 #x000334589D58> :ATOM :_NET_WM_STATE :STATE :NEW-VALUE :TIME 7044486))
    #<COMPILED-FUNCTION #:G39577>)
  NIL)
- 
#(NIL
  (:DISPLAY #<XLIB:DISPLAY localhost:0 (The X.Org Foundation R10400090) X11.0 #x000334527D48> :EVENT-CODE 28 :SEND-EVENT-P NIL :SEQUENCE 2027 :EVENT-KEY
   :PROPERTY-NOTIFY :WINDOW #<XLIB:WINDOW 1278x798+0+0 localhost #x02000006 #x000334589D58> :EVENT-WINDOW
   #<XLIB:WINDOW 1278x798+0+0 localhost #x02000006 #x000334589D58> :ATOM :_NET_WM_STATE :STATE :NEW-VALUE :TIME 7044486))
- :PROPERTY-NOTIFY
- 
(:DISPLAY #<XLIB:DISPLAY localhost:0 (The X.Org Foundation R10400090) X11.0 #x000334527D48> :EVENT-CODE 28 :SEND-EVENT-P NIL :SEQUENCE 2027 :EVENT-KEY
 :PROPERTY-NOTIFY :WINDOW #<XLIB:WINDOW 1278x798+0+0 localhost #x02000006 #x000334589D58> :EVENT-WINDOW
 #<XLIB:WINDOW 1278x798+0+0 localhost #x02000006 #x000334589D58> :ATOM :_NET_WM_STATE :STATE :NEW-VALUE :TIME 7044486)
<14/64> #<COMPILED-FUNCTION STUMPWM::HANDLE-EVENT>
- #<UNBOUND>
- #<UNBOUND>
- #<XLIB:DISPLAY localhost:0 (The X.Org Foundation R10400090) X11.0 #x000334527D48>
<15/61> #<ADD-ON-SYSTEM-FUNCTION XLIB:PROCESS-EVENT> 2
- 13844353/250000
<16/52> #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP-2>
- #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP-2>
- #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP-2>
- #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP>
<17/44> #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL-LOOP>
[41] unwind-protect frame
[36] catch frame for tag #:SIMPLE-RESTART-46527
- :LOCAL
- 0
- #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL>
<18/27> #<COMPILED-FUNCTION STUMPWM::STUMPWM-INTERNAL>
[26] catch frame for tag :TOP-LEVEL
- ":0"
<19/22> #<COMPILED-FUNCTION STUMPWM:STUMPWM>
[20] EVAL frame for form (STUMPWM:STUMPWM)
[16] frame binding environments
  VAR_ENV <--> NIL
  FUN_ENV <--> NIL
  BLOCK_ENV <--> NIL
  GO_ENV <--> NIL
  DECL_ENV <--> ((DECLARATION XLIB::CLX-VALUES VALUES OPTIMIZE DECLARATION))
[7] APPLY frame for call (:LAMBDA)
<20/4> #<FUNCTION :LAMBDA NIL (STUMPWM:STUMPWM) (QUIT)> 0
- #<COMPILED-FUNCTION EXT::SAVEINITMEM-1>
<21/2> #<COMPILED-FUNCTION EXT::SAVEINITMEM-1>
<22/3> #<SYSTEM-FUNCTION SYSTEM::DRIVER>
<23/3> #<SYSTEM-FUNCTION SYSTEM::DRIVER>
- #<ADDRESS #x000000000000>