If cloning using multicasting starts OK then gets slower and eventually disconnects, then it is usually an issue with the network driver. If you already have the latest version of the driver then there as still some things you can try.
Some NICs do a bad job of autodetecting the line speed and duplex settings for your network; this causes intermitted problems on the network. You can force it to use the correct speed and duplex by modifying the template settings in the Ghost Boot Wizard and adding the settings to the protocol.ini file. The exact settings differ from NIC to NIC, but documentation should have come with the updated driver.
Also, some DOS drivers do not work correctly unless the BIOS has set up the devices. Usually the BIOSes don't do this because they assume that Windows will do it after it boots. Try setting the "Plug'n'play OS" option in the BIOS to "no" and see if that makes any difference.