Error 49 usually signifies a firmware error (which could be due to a formatter problem), but it can, in some cases, be invoked by some system sending a 'rogue' job (not necessarily a conventional print job) to the device.
See thread http://h30499.www3.hp.com/t5/Multifunction-and-All-in-One/LJ-Pro300-color-MFP-M375nw-Power-cycling-displays-quot-49/m-p/6348735 which discusses similar symptoms (albeit on a different LaserJet model).