Here's the scenario: One PMac G5, one AthlonXP 3200+ system. Both computers are connected to each other by one CAT6 cable (straight, not crossover) with my Intel Pro/1000 card doing the Auto MDI/MDIX functions so the network runs without a crossover cable. When I try to transfer something large from the PC to the Mac, it transfers for about 10-15 seconds then it stops transferring. HD light goes off, the PC locks up sometimes (not always), and the time-till-transfer-finished keeps going up into infinity. I am not using jumbo frames since Apple decided to not implement that feature for some dumb reason into the onboard Gb ethernet. My Intel card has the feature but doesn't have it activated. The PC is running XP Pro SP1 and the Mac has 10.4.1. It happens also when I use a 100Mb 3Com switch isntead of a straight gigabit connection. The problem has never manifested until I got the Mac, so I'm thinking the onboard NIC is crapping out or something.