I'm seeing this issue as well - built a new 10.9.3 NetBoot image from a MBP Retina 15" and tried to then NetBoot the very same machine later on... failed with the same error. Image was pulled with Composer, then dumped into SIU and added as a NFS/Diskless Netboot volume.
According to the linked post, removing the /var/folders/ content fixes the issue, however I removed those using a script run before image capture... so that workaround does not solve the issue for me. There is a cool article about /var/folders here: http://blog.magnusviri.com/what-is-var-folders.html and an interesting tidbit related to the issue under "Default structure" where the writer noticed, "I eventually figured out that if I deleted everything in "/var/folders" and rebooted it would be fine. But after making some inquiries it appears that if "/var/folders" doesn't have the correct structure it could cause the error."
Am going though the process again w/o running my script to see if anything changes, however I doubt there will be a difference. Worst case, I'm rolling to 10.9.2 so I can get something working here (our 10.9.1 NBI is too old for the new stuff).
Update - ripping out /var/folders may have been the culprit in my case. I created a backup before running my script (which had the base image for netboot) and rolled back to it. Ran it through the image creation process -> composer to SIU, and it booted my machine fine this time. So as magnusviri.com noted, this could go either way potentially... there is a bugreport in at Apple regarding it already so now we play the waiting game or hope it doesn't exist in 10.10. Will probably roll through this once more with var/folders excluded from my script to see if I can still yank out all of the fluff and trim the image down to the bare minimum as before.
