I have had success with a remote connection using screen sharing with my father in NYC and me in MI with my MacBook Pro (on brother's network, not this one), but with my new 12" PowerBook G4 I can't get it working. My mom's eMac is set up correctly, she has the sharing preferences turned on. Under "Audio" in the iChat menu bar, it allows her to check off "Screen Sharing Enabled". While my PowerBook wont let me select that option, it's grayed out. I have the sharing system preferences setup correctly too. I have used this computer to share screens with the eMac on a local network (@ my mom's), but I have had no success with a remote connection so far from this network location. I have no firewalls turned on, just using a normal Netgear router, no password (for now). I shouldn't need to mess with port forwarding or triggering, my brother has the same router and I have had a remote screen sharing session from his network. What gives? Why can I not share screens from this network? I reset my router and went through the whole setup wizard and left it all default. Charter (ISP) should have nothing to do with this, they told me in the past that they don't block or limit any ports. 
Edit: Oh and of course we are both running the latest version of Leopard.
Edit: Oh and of course we are both running the latest version of Leopard.