orrzxzEnivobI figured it out. For some reason, my remote control program (Parsec) started causing Houdini to crash on startup. Funnily enough, starting it up, quickly disconnecting and waiting a minute before reconnecting allows Houdini to operate normally.
Maybe your overclock is unstable?
Saved my day you legend, can also confirm Parsec Virtual Display adapter seemed to be causing the same issue.
Thanks!