For some reason that I have not been able to identify, when I try to
select a range of adjacent cells using the Ctrl+Shft+Arrow Key
combination in the Formula Bar, rather than select the range of
cells I would like the formula to operate on, only the first cell in
the range is selected!.

Example worksheet range:

Col B
Row 1 10
Row 2 10
Row 3 10
Row 4 10
Row 5 =SUM(

1. I enter =SUM( in cell B5
2. I select the last cell in the range I want to sum - B4
3. I hit Ctrl+Shift+Up Arrow+Enter - Until today, this resulted in
=SUM(B1:B4) in cell B5.
4. For some extremely infuriating reason, the resulting formuala in
Cell B5 = SUM(B4)!!!!!!!!!!!!!!!!!!!!

This happens in all workbooks even when I restart Excel!

Somebody please please tell me why this happens and how I can fix it!