User does not respond

Question

Hello,
I am posting this question with hopes of a personal response from Ralph Johns or Defcom... seems like they are the resident experts on this business. If any one else has ideas I would be happy to hear from you too. I know that there are many other posts on this topic but I have tried all the stuff that I have read and I still can't connect with my dad.
I changed the streaming preferences in Quicktime, I opened the ports that are listed on the support sheet and turned the firewall off, I called into the AIM appleu3test01 buddy and got video back, and we have tried to viideo chat using a different program and were able to. My dad has done all the same things.
The messages that I am getting in connection doctor are as follows:
2006-02-19 13:04:02 +1100: [email protected] did not respond.
Tried to send UDP SIP "invite" to the following IP addresses and ports:
207.216.192.21:48994, 10.0.1.2:5060
2006-02-19 13:09:46 +1100: [email protected] did not respond.
Tried to send UDP SIP "invite" to the following IP addresses and ports:
207.216.192.21:49120, 10.0.1.2:5060
2006-02-19 13:14:40 +1100: [email protected] did not respond.
Tried to send UDP SIP "invite" to the following IP addresses and ports:
207.216.192.21:49148, 10.0.1.2:5060
Dad and I are both using OS 10.3.9 and iChat 2.1. I have a Siemens SpeadStream 4200 modem and no router and dad has a Dlink modem and an airport.
The very first time that I set up the isight I was able to do a one way video chat with him and there were no dramas. The next couple of times we started the video chats and after a few seconds it would cut out. Now we can't get anything at all. Unfortunately I do not know what the settings were when it was working and a couple of things have changed since then: I have since installed the iSight 1.0.3 upgrade and I have upgraded my internet connection from 512kbps Cable broadband to 1500kbps DSL broadband.
I can't think of anything else to try. Please help!
iMac G4 1GHz 17" Mac OS X (10.3.9) Running iChat 2.1 with iSight v1.0.3
iMac G4 1GHz 17" Mac OS X (10.3.9) iChat v2.1 and iSight v1.0.3
iMac G4 1GHz 17"   Mac OS X (10.3.9)  

Answer 1

Thanks for the advice guys... but I am not exactly sure which will lead to the quickest solution.
I went to the Speadstream setup page to put the modem into bridge mode as Ralph suggested. Under the Mode menu there were 3 choices: Optus Bridge (Optus is my ISP), NAPT and Full Bridge. Optus Bridge is selected, so I think that the modem is already in bridge mode??? If I changed it to Full Bridge mode it said that I wouldn't be able to access the setup page any more so I didn't do that.
I tried messing around with few of the other settings (ie. disabling DHCP) and I just lost my internet connection all together, so I am not too game to fiddle around with all of that again without some good solid instructions.
So at this point would the best solution be to change the settings on the Airport or is there an easy way to change my modem that I did not see??
Also when I followed the link to see how to change the Airport into a Wireless Access Point the page had moved... so if that is the solution please advise me on how to do that so I can forward it to my dad.
Thanks again for your help guys!