Hi deep! Thank you again!
That thread was a little outdated, the current gnome is 2.6. There is no more /.gnome/gnome file on my $home, but your post gave me the idea to search for the config in gnome's stuff, and I found it, finnaly!
You have to use this app, GConf, under System>More programs> Configuration Editor (this is kde launching a gnome app). Inside GConf there's a hierarchical tree, you should go to desktop > gnome>url-handlers>http, and there it is! Just edit the key.