Hmm.. that does indicate that you're trying to load a profile that's been deleted (just wanted to verify). Also, be careful with your spaces! There should be no space between the dash and the u in the gconftool command. On top of that it's load_prof, not load_pref.

To verify, you can install gconf-editor, and browse to /apps/rdesktopand check what value the load_prof key is set to. You can also edit or unset the key by right clicking on it in gconf-editor.