A similar thing happened to me:
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Timestamp   : 2011-09-24 12:09:27
Error level : CRITICAL
Message     : Player action exception!
Error message : Access violation
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Timestamp   : 2011-09-24 12:09:28
Error level : FATAL EXCEPTION
Message     : Fatal exception encountered
An unhandled exception occurred at $004810AD :
Exception : cannot resume non-suspended coroutine
  $004810AD  TLUACONFIG__RESUME,  line 107 of d:/Projects/fpcvalkyrie/src/vluaconfig.pas
  $00488609  TPLAYER__AICONTROL,  line 1083 of src/dfplayer.pas
  $0049DE07  TBEING__ACTION,  line 649 of src/dfbeing.pas
  $0049DF6C  TBEING__CALL,  line 675 of src/dfbeing.pas
  $0041E70A  TDOOM__RUN,  line 444 of src/doombase.pas
  $004022CA  main,  line 91 of src/doomrl.pas
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I THINK the last key pressed was 'f', but I can't be sure. Happened in the first couple of levels of Phobos Hell.
UPDATE: Happened to me again, in the same run, with the same error message. I think it may have something to do with saved games, as I used a saved file both times. Also, it's definitely not firing, it's strafing. I was pressing Numpad 9/PgUp.
UPDATE2: Happened again, while strafing with Numpad 1/End. This time on a clean game (no saves) and before Phobos Hell. The game also logged some additional stuff:
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Timestamp   : 2011-09-24 15:00:56
Error level : FATAL EXCEPTION
Message     : Fatal exception encountered
An unhandled exception occurred at $004810AD :
Exception : cannot resume non-suspended coroutine
  $004810AD  TLUACONFIG__RESUME,  line 107 of d:/Projects/fpcvalkyrie/src/vluaconfig.pas
  $00488609  TPLAYER__AICONTROL,  line 1083 of src/dfplayer.pas
  $0049DE07  TBEING__ACTION,  line 649 of src/dfbeing.pas
  $0049DF6C  TBEING__CALL,  line 675 of src/dfbeing.pas
  $0041E70A  TDOOM__RUN,  line 444 of src/doombase.pas
  $004022CA  main,  line 91 of src/doomrl.pas
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Timestamp   : 2011-09-24 15:00:56
Error level : FATAL EXCEPTION
Message     : Fatal exception encountered
An unhandled exception occurred at $00420AF9 :
EAccessViolation : Access violation
  $00420AF9  TDOOMUI__DRAWSTATUS,  line 560 of src/dfoutput.pas
  $00420521  TDOOMUI__DRAW,  line 434 of src/dfoutput.pas
  $0047EB38  TTEXTMODEOUTPUT__UPDATE,  line 148 of d:/Projects/fpcvalkyrie/src/vtoutput.pas
  $00448560  TUIMESSAGES__ADD,  line 874 of d:/Projects/fpcvalkyrie/src/vui.pas
  $0042D94B  TMESSAGES__ADD,  line 761 of d:/Projects/fpcvalkyrie/src/vrltools.pas
  $00420F7A  TDOOMUI__MSGENTER,  line 579 of src/dfoutput.pas
  $00441502  SAVE,  line 93 of src/dfsave.pas
  $00441872  DFSAVE_finalize,  line 147 of src/dfsave.pas
  $0040B2E9
  $004022CA  main,  line 91 of src/doomrl.pas
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