I am importing data from a text file and reducing it down to 2 columns; one
with names, one with numeric values. I save the file as an Excel workbook
and then proceed to edit the data. This editing involves sorting, performing
some deletions, re-sorting, etc. Sometimes for a reason entirely unknown to
me, the term [GROUP] appears at the end of the file name. When [GROUP] is
invoked, I can't sort the data.

What causes the status of my file to change to [GROUP] and how do I get the
file back to a 'normal' Excel worksheet (so that I can perform sorting on the
data)?