Hello João,
I discovered something today about the debug window problem I'm having with slime.
I have a little-used installation of Linux Mint 16 on a different partition of my hard drive and I spent some time today going through the steps to load Emacs 24.3.1, along with sbcl-1.1.18, and all of the other folders and files that it took to make it as similar as possible to my installation of Linux Mint 14. I had a little problem initially until I remembered to install quicklisp and then I downloaded a fresh copy of slime using my install script and started emacs-24, did M-x slime, and there was no unwanted debug window in emacs. I quit and restarted slime several times and each time it came up without the unwanted debug window.
It seems the slime debug window problem is specific to my installation of Linux Mint 14. I can only guess that I have done something to cause the problem, but I have no idea what it might have been. I'm usually very careful about installing anything that might cause a problem, but maybe I did something stupid...
Anyway, to make a long story short, I'm going to migrate my work system files over to the Linux Mint 16 installation and then clean up my work partition to use for the next new release of Linux Mint (I kind of like it).
If you are searching for the elusive debug window problem, I suspect you'll never find it on a different system so I suggest you cease and call it wasted effort because of me.
Thanks again for all of your help,
Paul Bowyer