Mozex doesn't work anymore with Mozilla 1.7 and Firefox 0.9. There is an alternate method that seems to be working with both of them:
(1) remove mozex
(2) insert about:config in the address bar
(3) right click on the list, select New, then Boolean; insert network.protocol-handler.external.ed2k as Preference Name and true as Value
(4) now another right click, select New and String; insert network.protocol-handler.app.ed2k as Preference Name and /usr/bin/ed2k (or path to where the file is installed on you system) as Value
now ed2k links will be captured by amule