copy paste formula repeats the sum total no maths going on

[DBenz]

Hi,
Excel 2013
It has suddenly started doing this:-
I add some spending in the september column., total box at base doesnt change, oh dear.

I do the click in the total box for august that is correct, click copy then paste formula for september and get the august total appear.
oh dear oh dear.

lets cleanse it, delete the totals boxes Jan to dec.
click and drag upward for aug and click sum, and get £150, correct.
look at the formula and its correct.
click the total box and paste that using paste formula into Jan through to July.

get £150 for each box, damn !

I have done this thousands of times since 1998 so know the method.

It has done this on another sheet.
and another and another, does it everywhere.

Its as if Excels brain has ceased working.

This is my finances workbook with hundreds of sheets. Its ceased working in effect.



NIGHTMARE.

Has it reached some kind of sheet and entry limit ?

My current account page is a few thousand rows long by now etc.

HELP !

DBenz