Set up using AMC AB15A100 drives, brushed DC motor Prototrak Plus with Encoders

Many, many thanks to all the members for a real informative forum.

Many thanks!

Hope all are well and staying warm!! I have been using my mill as usual (after installing the RAM (it had 512; I added 1 GB; now has 1 GB plus the 512, as memory)) this message would appear, my thinking was slot 1 does not match slot 2 in memory:

"Keys: Press F to fix the errors, I to ignore, S to skip mounting, or M for manual recovery"

I would press F to fix, but it would appear next time it was booted up.

Today after running a few different parts & was starting to open a new part from the USB, and it got hung up opening new part; a new message appeared on-screen:

Could not start the X server (your graphical environment) due to some internal error. Please contact your system administrator or check your syslog to diagnose. In the meantime, this display will be disabled. Please restart MDM when the problem is corrected.

Now has this on screen:
Linux Mint 17.3 Rosa cnc tty1
cnc login:

I have tried the login p/w & name, w/o any luck getting past this screen.

Please, all help would be warmly welcomed. Many thanks!

Edit:
After pondering, I pressed the power on button, for 5 seconds, computer went off, waited 15 seconds powered back up and all is good. There is still a message (not exact same) on start up, I did what was suggested, will try in the morning.  Many thanks!!