After some editing, I noticed that the formula bar in an Excel 2010 workbook no longer displays the formula, although I can still access the formulas by clicking on the cell. Any idea what I might have done and how to undo it?
Maybe you introduced a blank line before your formula?
If you click on the cell then move your cursor to the lower edge of the formula bar, the cursor should change to a double-headed vertical arrow. Drag this downwards so that the formula bar now displays multiple lines. Can you see the formula now? If so, you can just clean up the blank line above your formula and all should be good again. (Or simpler still, just delete anything before the "=" in the cell, but resizing the formula bar can be useful in other circumstances too).