iChat communication error! please help! ...

Hi,
I have tried to iChat with my Mac friends and PC friends, but it never works, it lets me IM them, but not video or audio chat. Everytime i send an invite, or they send me one, i accept but then a something pops up that says "communication error" and says like the other person hasnt responded when they have? It's starting to get really annoying. And i looked at the details and its says Date/Time: 2009-08-31 13:17:52.801 -0400
OS Version: 10.5.7 (Build 9J3050)
Report Version: 4

iChat Connection Log:
2009-08-31 13:17:17 -0400: AVChat started with ID 2510517345.
2009-08-31 13:17:17 -0400: chatt4liffe: State change from AVChatNoState to AVChatStateWaiting.
2009-08-31 13:17:17 -0400: 0x1a752340: State change from AVChatNoState to AVChatStateInvited.
2009-08-31 13:17:27 -0400: 0x1a752340: State change from AVChatStateInvited to AVChatStateConnecting.
2009-08-31 13:17:27 -0400: chatt4liffe: State change from AVChatStateWaiting to AVChatStateConnecting.
2009-08-31 13:17:43 -0400: 0x1a752340: State change from AVChatStateConnecting to AVChatStateEnded.
2009-08-31 13:17:43 -0400: 0x1a752340: Error -8 (Did not receive a response from 0x1a752340.)
2009-08-31 13:17:43 -0400: chatt4liffe: State change from AVChatStateConnecting to AVChatStateEnded.
2009-08-31 13:17:43 -0400: chatt4liffe: Error -8 (Did not receive a response from 0x1a752340.)

SOMEONE PLEASE HELP! Thanks!

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Orignal From: iChat communication error! please help! ...