For the question at hand, Edouard can you remove the shortcut from the command, by clicking the x that appears? If so, can you *now* enter the key combo you want.
I've already tried it, it was no use.
Oh yeah almost forgot, this doesn't really have to do with the LaTeX bundle, it's a question about key equivalents.
In fact, it isn't, but the problem appeared only with that particular function. Anyway, the problem was that the System Preferences > Universal Access > Zoom option was on (why it was, I have no clue) and that one of its shortcut are, on a french layout, cmd opt - (minus) and cmd opt ).
Thank you very much again to both of you for your help.
Haris Skiadas