Very seasoned in Excel - problem started with my last laptop, assumed the problem was there and could never resolve. Problem is now occurring on brand new computer, cannot find any solutions.
Occasionally while working in my active workbook, I'll no longer be able to edit cells or use arrows to move cells. I'll click on any cell, hit ENTER, and another inactive window that was open will come up and it will revert to the last open cell there as if I was hitting ENTER on that workbook. I click back to the original workbook and the problem is resolved.
This becomes a huge annoyance when it happens multiple times an hour, in the middle of my workflow - disrupting it 10-20+ times a day.