Mac Mini (2007 model) Ethernet and 802.11N dead

Question

Wow, talk about frustrating...my 13 month old 2007-model Mac Mini just crapped out with a couple of issues. The Ethernet networking reports the cable is unplugged, even though it's not, and the 802.11 wireless networking won't connect at N speeds. Of my four Macs, this was the only one without AppleCare, so no warranty help to be had.
Anyways, to troubleshoot the system, I've verified that the Ethernet cable I am using provides connectivity on another machine, and that other machines in the same workspace can connect to the 802.11n router via "n" speeds. So it's not anything external to the Mac Mini.
I also booted from a different OS X version via external USB drive, and the Ethernet and Wireless "n" still display the same symptoms. So it sounds like hardware, since a software glitch shouldn't appear with a different boot drive, right?
Verify disk and repair permissions also performed, with no anomalies noted.
System Profiler shows the Ethernet port is there, but in following troubleshooting "cable unplugged" errors tips in another thread I tried removing it from the networking pref pane, and re-adding it, but Ethernet doesn't show as an addable option anymore.
I am able to connect via 802.11g, so the machine's not totally dead connectivity-wise, but as home theater media server, I am sure going to miss the rapid file transfer rates of Ethernet or "n" wireless.
So, before I write this machine off as crippled, can anyone think of anything else I might try to get Ethernet working again? I suppose a USB-to-ethernet dongle would be better than Wireless-"g", but it's still less than ideal.
On another note, oddly, several of my programs started complaining about not being registered, which is what lead me to try permissions and disk verifications. Pretty strange.
Any ideas appreciated.

Answer 1

Ah, you're right about the N not being supported. Color me stupid on that one...silly me assumed that since I'd only had it a year, and N was around on my other Macs purchased around then, that it was there, but of course the design was a year old already. I'll update the thread post to drop that part.
As for the cable, I sort of tried two other cables already. My actual setup is to run the Mini to a gigabit switch, then the switch runs a CAT6 cable 50' to the router. I used two different cables out of the switch, and then plugged the long run directly into the Mini. No go. I guess not a big issue to unplug the Mini and move it to another room. I'll give it a go, but take note that it's been working fine on this same cable/switch/router set-up for a year. Odd that it would suddenly change.
Thanks for the tips, I'll post back with results when I get home and can check it out.