Hello,
Does the BIOS of that system board support a native mode as well as a compatibility mode for the SATA hard drive?.
If it does support compatibility mode, I would definitely give that a try.
If not, I would consider trying the -FNI switch setting as a test.
If you are able to image 1 machine at a relatively high speed, then it would appear to be an issue with the packet driver interface on the NIC not correctly responding to multicast frames.
What kind of switch / hub are you using to perform imaging?.
If you find that one machine is still relatively slow (<100mb on display of GhostCastServer), then I would start to think that there is a conflict between the NIC and the SATA drive.
Adding information such as the model of switch you are using might be able to help others help you with this issue.
Thanks,
Alex