1 Gb NICs but only 2 simultaneous vMotions?

vCenter and ESXi 4.1

Cluster 1 - 3 x HP 360 G7 Servers; 6 x 1 Gb NICs

Cluster 2 - 3 x HP 360 G5 Servers; 6 x 1 Gb NICs

Virtual Distributed Switch - port group for vMotion

Background: Cluster 1 originally had HP 380 G7 servers but were repurposed because of they had lots of local storage. I replaced the 380s with 360s.

Problem: The new 360s in Cluster 1 will only perform 2 simultaneous vMotions. Cluster 2 will perform 4 simultaneous vMotions. All hosts in both clusters are using the same vMotion portgroup on the same vDS.

Troubleshooting:

1. I have confirmed that all physical NIC adapters are set to 1000 Full via vCenter and on the console with the esxcfg-nics -l command.
2. Confirmed that the access switches are negotiating at 1000 Mbps.
3. Looked for differences between Cluster 1 and 2.
4. Reviewed this thread: http://communities.vmware.com/message/1788364

Is there anything else I can check?

Thanks in advance!