Gigabit direct connection Intel 82566 DC 2 & Vista

When it locks up again, you might try disconnecting the cable for a minute or so, and then reinsert it, and see if that avoids the reboot.

Thank you Stephen! Next time it blocks I'll try to disconnet for a minute !

I am thinking you should open a support case with Netgear, and have them analyze the logs, etc. before you start buying network stuff.

I've already opened MANY case with Netgear Italy. I have this problem since I've bought the NAS (July 2011). They sent me a new RAM bank,
they told me that it was failing sometimes. It seemed to work, but I didn't stress the NAS too much in that period (two month ago).
When I started to use the NAS intensively the problem was still there.

Now they have suggested me to reinstall the firmware (?), I've tried, but of course nothing changes... Now they tell me to make a factory reset,
but I'm quite sure that this is a network problem...

This lockup might be caused by something else (a failing disk or chassis) that is being provoked by the higher speed connection. Though of course you are still seeing some network issues (receive errors, symbols errors) which are not normal.

That could be, of course ... But the device seems to be healthy when the NIC blocks (normal reboot pressing power button).
With a traffic analyzer I can't see answers from the NIC. If there is a faulty drive I can't understand why the NIC does not
respond to a simple ping !

I am also thinking that if you do not have a current backup of your data that you should try to make one.

I do have a backup, but I use the NAS for my photography works, I can't stay with only one copy of my works, It's too risky.

Today a friend of mine lent me his gigabit card, with another chipset. That will be the next step...