ok, this happened again today.
Only difference this time was a kernel update via mint update manager earlier today.
Kernel 4.4.0-42 (level 5) update installed then switched off laptop to go out.
Came back to laptop a while later, switched on and froze again at plymouth splash.
Tried the above key combo and screen kept scrolling..cryptoswap stuff continuously for ages.....
Hard power off and booted into grub.
After a couple of attempted boots on 4.4.0-42, I gave up and reverted back to 4.4.0-38
I've also removed kernel 4.4.0-42 from my system via mint update manager/ kernel update manager.
switched laptop off and on and all is good again.
