no video or screen sharing on iChat 4 ...

Hi, like many others, i'm experiencing problems with audio/video calls and screen sharing on iChat 4.
It's really important since my dad lives abroad and is 80 years old, so i need to help him out by taking over control of his MacBookPro when he needs me to.

Here's our setup when it DID work:
We were both in my house, on my network, through my Airport Exreme. We're both running 2009 MacBook Pro's with OSX 10.5.8 on it, and were signed in to iChat through our google account (jabber).

Then he returned back to his home (i'm in Holland, he's in Austria), and since then we can only do text chats on iChat. Whenever we invite eachother for video chat or screen sharing, we get the same error message about a communication error, or telling us the other one 'didn't reply' or something like that. I'll copy-paste the exact message error details the next time we try.
We tried to solve it by changing services, meaning i signed in through my @mac.com account and he signing in through his AIM account, but with no luck. Also AIM to AIM didn't help.

I'm still on my Airport Extreme, connected to a DSL modem which is branded by my provider, so no idea what it is.
He is on a Speedtouch ST585 wireless DSL router, which he also got from his provider.

Any settings we should check/change? i've read all sorts of stuff about port forwarding, SIP/NAT compatibility and UPNP but that all works rather confusing than clarifying..

Any suggestions would be highly appreciated.

Thanks,
Lexxy

Message was edited by: TheRealLexxy

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