Is flow control enabled on

[Aaron Ledger]

Is flow control enabled on each NIC (WHS and WMC)? If you have a Gigabit NIC, flow control is especially important for the transition to FastEthernet.

NIC is one potential problem point and there are many problem NICs, unfortunately (e.g. Realtek). The switch is another potential problem point (converting between Gigabit and FastEthernet at the switch requires enough memory in switch to account for the potential burst of Gigabit traffic it may receive and have to send out at slower FastEthernet rate).

Forcing your NIC to FastEthernet speed instead of Gigabit could help. Reducing other traffic on the switch could help.