iChat Communication Error Help!?

In my family I'm the "electronics guru" this any electronic computer, tv etc problems fall onto me. I gave my Uncle my old iBook G4 circa 2005 and I'm teaching him how to use a computer. He has never used on before. It's strange to me but I'm still responsible for teaching him. I'm having a problem though. He lives in Florida and I live in Pennsylvania, and it's getting harder each day when we advance to a next step in the learning process to do it by phone. On a daily basis my girlfriend and I use iChat screen share to show each other stuff and what not. I thought this would be the genius way to show him how to do this instead of saying via phone. The problem is it keeps saying communication error when we try to screen share. He has lower end DSL at his house. I'm not sure exactly what is upload/download speeds are. I know the problem is somewhere on his end. He can connect to the internet fine, it's just when it comes to video conferencing and screen sharing the error pops up. I been trying to figure out what's causing this and being over 1000 miles away its hard. Does anyone know what some common problems could be. I know the firewall in OS X is turned off. If anyone could give me some tips of what I could have him try it would be great. Thank You!