MSM = Mass Storage Mode. Does it get seen by updater.exe in pre-boot mode? If so try flashing it back to US without a cure.

It may be that there's a corrupt file on board if it still plays up with US and can't access MSM still. Cure fw allows MSM so you can access the internal files system to either remove problem file/s, or reformat it entirely using RMPrepUSB. QuickCure3 doesn't always work as it's quite generic rather than unit specific, but in my understanding of the principal behind it is if does work then Cure3 would definitely work too. I always try QuickCure first though. I only just now un-bricked a 1450 on which QuickCure wouldn't work even though i've used it before on various units numerous times successfully. It probably depends on the reason for the unit not booting and whether the unit is getting partly into the boot process or hardly at all.

In your case, it's booting so QuickCure may work to allow MSM, but if it doesn't use Cure3.