Had my first "uh-oh" moment going from 1.23 -> 1.24 earlier today.
After I thought it had hung during the firmware download the PC finally rebooted, but then I got a Boot MGR is missing error. Panic!
Restarted again, same thing. So this time I powered the PC off, and turned it back on. The drive was now listed in the AHCI part of the boot up process, but still it said that Boot MGR is missing. Finally, went into the BIOS and found it had shifted the drive from 1st boot device out of my 3 HDD's to the last one. I moved it back, and all was well.
I haven't had that with the last two firmware flashes... very bizarre!