Thank you for sharing your solution, but my FileVault is not even turned on and my MBP 10,1 (15" mid 2012) shows the same problem, anyways: the loading process stops when the progress bar reaches 3/4 of its length, at startup. I have installed the NVIDIA Web Driver (which is alternative to the one automatically installed by OS X). The problem persists until I reboot and restore the PRAM (cmd+option+P+R at startup), which basically means reverting back to the previous driver, which makes the NVIDIA gpu useless and the Mac only works with the Intel graphics card !
I read somewhere that High Sierra is the first Mac OS that sets 10bits for something related to the graphics (I am sorry to be this general, but I don't know more), while the Web Driver is still using 8bits, so this may cause the problem we are experiencing. I don't know how to set that value to test this out, so I can't be sure about this.
For now, I can't run any CUDA programs and my NVIDIA graphics card (GeForce GT 650M) can't be used by the system, although I can see it from System Report - Graphics/Display .
If anyone has a solution for this, I would really appreciate it.
Thank you, have a nice day.