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Another update: A friend had just come by with his PowerBook. He can connect to both my Macbook and G5 and they both connect to his PowerBook. So why the **** can my 2 comps not see each other!!
 
Well, for anyone following this! After a third lengthy phone call to Apple stage 2 tech support I have been told there are known issues with 10.4.8 on Intel machines and some 3rd party routers. I am kind of relieved to hear this after weeks of self-diagnosis which has got nowhere.

Without me even asking, they are sending me an Apple Extreme base station (presumably one of the old 'g' protocol ones) free-of-charge which I can keep if it sorts out my problems with filesharing.

So I'm happy - at least will be if this works out!
 
Interesting result, particularly if it turns out that they sent you one of the new models of the router. I was aware of problems with the new Intel machines and wireless networking but was under the impression that this particular bug was fixed in an update to the Airport software around Christmas. This I remember distinctly since I had been unable to connect my new MacBook Pro to the wireless network of a hotel that we were staying at (well, it could connect to the network but was not receiving a valid IP address) but after the release of the update I could connect to non-Apple routers without trouble.

Still, free is free and you can't argue with that so I hope that this sorts everything out for you.
 
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