One other user experienced a bad connection with the edge connector of the circuit board with the processors and hard drive on it.
It cured on other users problems with his new machine!
I'll bet I'm the other user you're talking about !
Reseating the card & memory got me past my initial network I/O problem, but I've had several lockups and a couple of "reboot/call support" error codes. I'm scheduled to have an engineer give me a call to sort this out.
Here's a trick I learned from a support tech today. To get to the diagnostics menu (ps model, I assume this works for non-ps as well):
Power off via the Power button on the front panel.
Press the Up Arrow and the OK button and hold them down.
Keep them pressed and press the Power button and hold all three for 5 seconds.
Lots of interesting stuff on this menu - play at your own risk!