1. It's not normal. Maybe it's been a long time since you used anything other than Lunix. Unless the host server is offline or has a flaky connection, network drives should stay connected.
2. "Somewhat expected"? What are you, an Intel apologist? Then explain why they can be separately disabled in BIOS? It's a bug by any reasonable standard.
3. I've had four total DZ77GA motherboards and EVERY LAST ONE OF THEM DOES THE SAME THING. I finally gave up and stopped using the 82574L, I bought an external NIC by another company and my lockups mysteriously went away. The easiest way to repro the issue is due a large file transfer (say 100GB) over the 82574L--the lockup will happen very quickly. Does not happen using the other NIC or an external NIC using the same network equipment.
If you work for Intel in any capacity you should be fired for incompetence. Either way you should never post on these forums again. All you are doing is misinforming users and trying to sweep Intel's failures under the rug. You obviously have no experience with the DZ77GA, which since it is explicitly named in the thread title means you should never have had the balls to attempt to inform anyone of what was "really" happening.