If you are finding your GTalk connection in ur IChat getting timed out every 15 seconds with a message saying 'IChat lost connection to jabber account xxxx' , you are not alone. After some tiring search in google to resolution, I found the following work around.
Go to your IChat preferences, select your account and uncheck use my computer name check box.
I dont think any human being with a normal mind can guess this workaround but someone managed to find it.
Hope this helps.