Can't boot notebook at all anymore

[MR ZenWiz]

Before it was just a problem with the SSD.  Now the notebook refuses
to boot at all.

It keeps coming up in busybox, but the more command doesn't wokr, or
pieps don;t, so i can't peer through dmesg to see what's wrong.

This is an ASUS N75SF that was running Xubuntu 16,04 just fine until
this weekend.  (Last weekend it worked perfectly.  I even watched a
couple of movies on it,  Now it has gone completely defective.)

It was saying it couldn't find /sbin/init, and the best advice I could
find was to reinstall the OS, so I did that.

Now it comes up in busybox and there do not appear to be any errors at all.

Is it possible the motherboard just went wacko?

I ran the disk test and everything seemed to be fine.  I was able to
mount the drive from a live CD boot, chroot and update-grub, and still
no boot.

After the reinstall, still no boot.

It runs just fine from the live CD (actually a USB3 flash drive).

The only change I can think of that might have impacted this was I
changed the memory from 8GB to 16GB.   The last time I ran the memory
test, it passed.

I really don't want to have to get another laptop and write off this
one - it already cost me close to $500 I can't really afford to throw
away, and don't want to.

Suggestions?

Feeling VSF.

MR