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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