|Considering what you've done to troubleshoot I'd say there's something wrong with the hardware itself.|
If the system is no longer under warranty (and I suspect it isn't or you'd be calling Toshiba support) I would say try another network interface. If your laptop has PCMCIA slots (should have two) you can get a PCMCIA card and slip it in.
If you go to a reputable computer store (not an electronics store like Future Shop, but a real computer store) you should be able to get them to test a NIC out on your laptop before you make the purchase.
If you can't do that, make sure you hang on to the bill so you can return it if it doesn't work. But my preference would be to try it in the laptop at the store before buying.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.