[2010] contacts - Group by

[Ammammata]

I have 177 contacts with Company field empty, plus 200-more where there is
something inside

I click Current view, Manage views, List, modify, group by: here I select
Company, ascending

Then ok, ok, ok and all contacts are grouped BUT...
I have TWO "Company: (none)", the first has 74 items, the other has 103

The field Company is empty in all records

The first funny thing is this: I take one of the items in the "first"
(none) group, I put a fake company and save and it moves alone in its
group, then I remove the company and save again and... the item moves to
the "second" (none) group
Second funny thing: I take one of the items in the "first" group, I press
the BACKSPACE button but it doesn't delete anything since it's at the
BEGINNING of the field (and makes a beep, too), then confirm with Enter:
the item moves to the "second" group
Last funny thing: I take one of the items in the "first" group, I press the
DELETE button but it doesn't delete anything since it's at the END of the
field (and makes a beep, too), then confirm with Enter: the item remains -
correctly - in the "first" group

Any tip is appreciated