Premieres are much faster than HDs. I have both and I have not had any freezes during transfers.
It sounds like your HD's ethernet connection is being over-run. There may be some incompatibility with the switch that your HD is plugged into (or some bug in the HD's ethernet driver). Try a different switch is all I can say. There should be no routers/firewalls between your Tivos. Also check that they are locking at 100mbit Full duplex.