login mess in Mint/Mate

[Dave Stevens]

I tried to do a large (450GB) backup from a SATA disk hosting a Mint
Mate setup to an external 1TB SSD over usb3. It did not completer and
gave a "no space on device" error. The device turns out to be the SATA
spinning disk.

Now when I try to boot from that disk the startup stops at the user
login GUI screen. I have the login configured to not require a
password - i.e., there is one but it isn't needed there. 

As soon as I touch the keyboard the screen clears and after a delay of
perhaps 10 seconds I'm presented with the login screen again but this
time it sits for only a second or two like that and then repeats,
looping, apparently indefinitely, no matter what I do at the keyboard.

Does anyone have experience with this? Or can someone please suggest
what logfiles may be relevant?

TIA

Dave

-- 
Sometimes I wonder whether the world is being run by 
smart people who are putting us on or by imbeciles who 
really believe it.

Mark Twain