Ichat Tiger Problems


I have recently started using an ADSL Broadband internet connection with Telstra in Australia and have upgraded my eMac to Tiger OSX 10.4.2. The problem I have had when iChatting to friends in the UK who have Macs is that my frame rate starts at around 15 when the iChat commences and then reduces to 1 fairly soon after. This results in a blocky picture of me being transmitted to my friend. The picture of my friend however is OK. He is also running Tiger. I initially thought it was a problem with the port forwarding on my router (a Siemens Speedstream 4200) so opened the iChat ports. This seemed to fix an earlier problem that was blocking all of our chats, but I am not sure what to do now?

Another problem I am experiencing is with PC users in the UK. We can see each other's icons, but when either side initiates an iChat and the other side accepts, the message " xxxx did not respond " comes up. Any ideas???? I have contacted Apple, who said it was an ISP problem, and Telstra have said that it is an Apple problem... PLEASE HELP PLEASE HELP PLEASE HELP PLEASE HELP PLEASE HELP