That sounds like a windows resources problem. Try defragging, rebooting and shutting down everything except AutoCAD. Or the problem may be exactly as described: insufficient physical RAM to run AutoCAD as well as all the windows bloatware, and copy and pasting. Have you tried using wblock to extract the info from one drawing and inserting it in another, rather than copying and pasting. Also running in SDI = 1 may reduce the amount of resources AutoCAD requires and enable you to complete the copying