IChat used to work fine but not any more - suggestions?

Question

I've used iChat for about 1 year very successfully but recently video chat has stopped working. I have a MacBook Pro that doesn't work and a PowerBook where it still works fine.
Both have the same system and iChat software. Both are on the same wireless network. The Powerbook can connect to collegues and also the Apple test users (appleu3test01, 02, 03 etc.) while the MacBook Pro no longer connects although it used to connect just fine.
Symptom: I've tried having the MacBook request a conference with the PowerBook and the PowerBook never realizes that the MacBook requested a conference. When I try to initiate the conference from the PowerBook to the MacBook the MacBook never acknowledges that there has been a request. If I try to connect to appleu3test01 iChat on the MacBook displays
"Waiting for response..." for as long as I leave it the request window open.
It seems my MacBook Pro can no longer initiate nor recognize a video chat. (text chat works fine)
Given the above situation I have not tried to modify my router settings nor look into what my service provider might be doing - after all, everthing is still working great on one of my Macs.
All I have done is to try the old school Mac trick of deleting preferences. Specifically the com.apple.iChat.SubNet.plist, com.apple.iChatAgent.plist, com.apple.iChat.plist plists. That made no difference.
If anyone has any suggestions for me I would be very grateful.
Thanks in advance

Answer 1

I share that funny feeling but:
10.4.3 is to long ago for me to know whether it is within reach of the backward compatibility specifics of 10.4.10, the machine specifics, the routers settings and it's performance in combination with the italian provider and the policy they have towards their subscribers. Just to give an example, apparently the Powerbook does video chat, the MacBook doesn't The QT version that currently is downloadable has system requirements that ask for 10.4.9 as a minimum. And that is just a detail.
A little change to your settings could solve this, but I advice you to to a reset of your network hardware, and update them one by one to the current release versions of their hard (firmware) and software. Check the site of the ISP and router for advise on their current network mode. Write down their details, and your required input network access. Unplug the devices. Leave them a good 15 minutes to power completely down. The device that comes first in contact with the internet connection needs to be plugged in first. Wait till the lights are blinking stable, now connect your MacBook Pro direct to the Ethernet port of the Modem (?) and log in to the interface of the device by typing it's IP address into Safari. Choose easy set up, and you will be asked to input the information you have previously checked on your ISP's site. Check if the firmware corresponds with the version you looked up on their site. It probably will mention if there is new software available and it will take a minute. After the device has restarted, connectivity is confirmed. Click an internet site in safari, and walk through the network diagnostics windows to set up a stable network conform ISP advice. Now the second mac needs to start, select a site in safari, if it needs diagnostics it will ask, respond in accordance to join the network you just have set up.
Some possible trouble causes to look at as well:
Channel settings used by the american sold Extreme is not set to a number that the Italian bought Express automatically switched to as interference was eminently asking for. (Or vice versa and variations on the theme)
Encryption running on the MacBook Pro could cause the problem etc.
The MacBook Pro has an Extreme card. The Powerbook has an Express card.
The Extreme is limited to the performance of the Express now.
Check the help feature as well, open iChat, select help in the top menu.
You need to have a valid internet account, and current up to date software & firmware.
Hope it covers your issue but if it is not solved please post back: Firewall or router settings are likely to cause these problems as well. I am not very good at those.