Fatal Error?

I think it means you are not allowed to replicate an entry. (in CR4)

Ok The error is that the processor can not carry out the next instruction because the memory address it has to read from/write to is in use by another piece of the programme. Or another piece of software is conflicting and obstructing the next instruction in Auto Cad, this causes a conflict to be flagged and the error message to be displayed. I expect some bright software boffin will put me/you right as to the exact causation of this disruptive message. PS to CR4 editor Boffin is a valid spelling. Spell check highlighted it as not valid.

It may be because a particular shared resource (DLL, Drivers, etc) may not be as expected by Autocad. That means that Autocad may need a different version which includes Autocad specific functionality and which is not detrimental to other programs.

Recently installed hard or software may be the cause of your problem.

You could try to reinstall Autocad and hope that the unacceptable code will be replaced.