Mavericks NetBoot Image won't boot (access denied symbol)?

I'm starting the process of creating some new NetBoot Images to support Mavericks and I'm having boot issues that I've never come across before (I've been building NetBoot images for years using using OS X 10.4–10.8). I always make sure to use the latest OS version available at the time to support our latest hardware (mainly iMacs and Mac minis).
Right now, I'm using a Mac mini (Late 2012) running OS X 19.9.3 (13D65) to build a Mavericks-based "Tool Kit" NetBoot Image (for drive recovery tasks, drive repairs, etc.). Using the same process I've always followed, I've installed/configured the Mavericks "Tool Kit" system (also OS X 19.9.3, build 13D65) itself on an external FireWire drive attached to the Mac mini, then run System Image Utility (10.9.3, build 677) from the Mac mini (internal drive) to then create the NetBoot Image (using the system on the external FireWire drive as the source).
Everything proceeds as normal, but when I load the image onto my NetBoot Server (OS X Snow Leopard Server, dedicated to NetBoot), client machines fail to boot off the image (they attempt the NetBoot, but get the "Access Denied" flashing symbol. Normally, I'd get this when trying to boot a system pre-installed with a newer version of the OS than exists in the NetBoot Image (or, when the hardware requires a hardware-specific OS version, which isn't what the NetBoot Image is running), but that's not the case here (as I'm able to successfully boot these same machines using my 10.8 "Tool Kit" NetBoot Image).
As well, I'm able to boot these machines from the Mavericks "Tool Kit" system via the FireWire drive directly. So, hardware is "capable" of booting the system I've built, but not when attempting to boot via my NetBoot Server.
So, I'm wondering if anything has changed with Mavericks that would result in Mavericks-based NetBoot Images not being able to boot from images served from Snow Leopard Server? Honestly, I don't think this is the case though, because I'm able to serve DeployStudio-created Mavericks-based NetBoot images (served from the NetBoot Service running on this Snow Leopard Server box) to these same machines, without issue. The the DeployStudio created image was built using the same "Tool Kit" system as a base for the image creation. So, it really doesn't seem like an issue with Snow Leopard Server nor the Mavericks base-system I've built to create the images—it seems like it's an issue with the images created via System Image Utility.
Anyway, I'll continue my trouble-shooting, but if anyone has any advice, it'd be greatly appreciated!


In this discussion it is said that 10.9.x does not NetBoot on certain models due to a microcode issue.