How exactly does the icon in the bottom right hand corner look?
Like this

or like this

?
The first one means that you have a high ID on the ED2K network but that Kad isn't connected. The second one means the opposite (not connected to the ED2K network, but high ID on the Kad network).
As you describe your problem I would guess that you haven't opened every port aMule uses.
Have you opened all the ports mentioned
here (in partcular UDP 4665 (TCP PORT + 3))?
[edits]For some reason it seems that the link above doesn't work and I can't get it to work. Anyway I'm referring to
this wiki page, chapter 8 and 9 from the table of contents.[/edits]