Did you use a machine specific build of the OS? Check the build number 12D78 seems to be the universal build number in our shop.
No and we have the same exact build number 12D78.
When this happens to me, I've been able to hold down Option at boot up and choose my NBI from there and then it seems to work.
We're actually only doing that for newer machines so I can ensure people are using the correct nbi.
Same here, we've actually created NBI's for the different models (using the latest release) just in case our "agnostic" NBI doesn't work. Currently some (but not all) MacBook Air and iMacs don't boot from the Default NBI, so our imaging folks need to hold OPTION key to select the appropriate NBI. So forcing NBI's based on model doesn't seem to work.
Meh...who ever said Apple was an enterprise company. :(
You folks realize you can Verbose boot (Command V) when NetBooting, right? I've had some issues trying to serve images from OS X Server 10.8.2/10.8.3 via http, changing them to NFS seems to always work...