Mmmm, weird. I've just tried, and it worked for me (using Tiki 2.2):
I can see the list of mods after I click on "update remote index" at admin mods, and after this message:
Can you try again?
BTW, which Tiki version are you using?
for completeness, at "mods configuration", you should have:
Mods local directory: mods
Mods remote server: mods.tikiwiki.org