NetRestore image fails to install, no reason given

I've got a Mac Mini running the latest version of OS X Server, and two iMacs. Both iMacs are the same model (Mid 2007 20-inch, 2 Ghz Core 2 Duo). On one of the Macs I have installed 10.9.4 and installed all of our software, and I used it to make the NetRestore image on the server. I've tried the image on other (newer) Macs around and it seems to work fine, but when I try to run it on this second iMac (which is identical to the original iMac that I made the image from), it fails. Does anyone have any ideas about what might be going on or how to go about fixing it?