|My guess is that the problem wasn't really solved specifically by changing the view from Normal to Page Layout, but merely by the change in view as Mike hinted at.|
A quick test would be to toggle back and forth between Normal and Page Layout and see if the multiple column selection problem returns and goes away with each toggle of the 2 modes. I'm guessing it won't.
My guess is that you were a victim of the annoying "multiple cell selection" bug that showed up in Excel 2007 and beyond and changing the view cleared it up for the time being.
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