Try the following:
Click on Tools|Options, and then, on the View Tab, Under Window options,
tick the Formulas option

"ALK" wrote:

When I doubleclick on the formula to see its components, the usual "borders"
around the precedents do not appear.

The formula bar on top still shows the formula, but without familar borders
it is so much more time consuming to edit the cell.

Any ideas why it happens and how I can correct it?

Thanks!!