» For a bit tutorial how to downgrade Lion back to Snow Leopard OS X please mind that Snow Leopard install erases your partition. Backup before you do. A simple tip if you have enough space: repartition your drive, make 2nd partition for Snow Leopard, install it there. I had no space, so I had to restore user data from backup.
Since the office can’t longer bear Ready NAS NV+ hangs and network outages invoked by accidental Lion OS X “casts of death”, I am forced to downgrade Lion. And it is indeed painful.
I urge everyone not to use a machine “updated” to Lion together with ReadyNAS NV+ in one network. Even with 4.1.8 software it has severe problems. For now there is no 100% cure.
UPD: Fresh Lion install from scratch was painful as well, but it seems solved the problem. Something evil still lurks, however, in printing drivers for HP and Samsung. Unfortunately I lack knowledge to debug their tricks.
UPD2: Yay! @chirpah pointed right. Enabling jumbo frames on ReadyNAS NV+ solved the puzzle.