ExcelBanter - Strange behaviour when sorting rows

Hello.

I have a spreadsheet divided into two sections. I've used the first seven
lines to summarise the data contained in the rest of the sheet. The eight
row is used to define the column data labels, and the actual data is
contained in rows nine onwards.

The strange behaviour I've noticed is that when I sort on any of the first
three column data label on the data label row, the first three columns are
correctly sorted, but the other columns are left unchanged! The same applies
for the other columns: sorting on any of these has no effect on the first
three columns. It's almost as if the bottom half of the spreadsheet has been
split into two separate halves. This has the side effect that the data
summarised in the top section depends on how I've sorted the rows below!
I've tried using Data-Sort, but this hasn't helped.

As a final experiment, I removed the top section, so that the first row is
now the data header row. Made no difference.

I'm sure that I'm doing something stupid. I've used this before, and it
worked, but this spreadsheet is based on a file I received from a colleague.
Could there be special formatting embedded in the file?

Can anyone help me?

Many thanks,
Paul