@LNewt3 & FrankOlsen1:
Is your CPU overclocked or not? I tried a few things to get my X99S MPOWER setup working with 1809 to no avail (modifying BIOS and mcupdate_GenuineIntel.dll). In the end 1809 just doesn't like overclocking when using a X99 chipset.
Running with stockspeeds, I have no problems upgrading to and running 1809; it's only if I overclock (OC Genie or manual overclocking) that my MSI system is hanging right after booting...
So I wonder whether build developer preview 1904 really fixes this problem or maybe that you guys just reverted back to stock speeds by accident?