It occurs after the mortem, and i was wrong- it happens when you Q-Y, leave or die, EVER.
Error.log entry:
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Timestamp : 10/03/2012 22:29:18
Error level : FATAL EXCEPTION
Message : Fatal exception encountered
An unhandled exception occurred at $004B87F0 :
EAccessViolation : Access violation
$004B87F0 TLEVEL__PROPERCOORD, of src/dflevel.pas
$004C33D9 TDOOMCONMAPUIELEMENT__ONREDRAW, line 165 of src/doomui.pas
$00429428 TDOOMIO__LOADPROGRESS, line 617 of src/doomio.pas
$0041E1E0 TDOOM__LOAD, line 135 of src/doombase.pas
$0041EAA4 TDOOM__RUN, line 267 of src/doombase.pas
$00401B15 main, line 71 of src/doomrl.pas
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Also, just for laughs, 0 out of 0 is exactly -1.#IND%