[eschwartz]

All you need to do is start calibre with the command "calibre-debug -g" and optionally redirect that to a file.

I use linux, so it is easy to override calibre's startup command with a shellscript in ~/bin/calibre :

#!/bin/bash

if [ $# -eq 0 ] || [[ "$1" = "--detach" ]]; then
    echo -e "\n\n\nStarting calibre at $(date).\n\n\n" >> /tmp/calibre-debug-$USER.log 2>&1
    calibre-debug -g 2>&1 | tee -a /tmp/calibre-debug-$USER.log 
else
    /usr/bin/calibre $@
fi
[eschwartz@vostro ~/git/pkgbuilds]$

On Windows, you will have to start calibre from a batch file "calibre-debug.bat":

calibre-debug -g > %TEMP%\calibre-debug-%USERNAME%.log

And make sure to always start using the batch file.