Posted 26 January 2010 - 08:16 PM
Not sure but it sounds like the MacBook airport card is running at b or g speed, and the router is slowing down to accommodate it. This used to be true of the old Apple Airport routers; they would run at the speed of the slowest card accessing them, so even if you pro was running 802.11 N protocols, if another computer on the network was running 802.11 B everything would throttle back to B speeds.
Don't know how to check the specs on your router. Is Telstra the wifi router or the service provider?
On the Macbook you can check to see the modes available to the airport card by going to the Apple menu, clicking on "About this Mac", then "More info", then look in the column list for "Airport". Click on that and it will show you both the mode for the airport card (the Macbook) and the network mode or PHY. If either is running at less than N or G, that will be the problem. Trouble is, I don't know what to tell you to fix if one or the other is running at B mode speeds. I believe airport cards are supposed to auto negotiate the fastest speed, and I don't know of a way for that to be manually reset.
If the Macbook is running at B or G speeds, try it on a different network and see if it does the same thing. Some wifi routers use a non-standard implementation of the N protocols which other wifi equipment may not be able to communicate with. If the MB connects to a different network at N speeds, then it could be incompatibility. If the Macbook can't get above B mode on any network, it may be a faulty airport card.