I am using a spreadsheet with different formulas that I use for business
purposes which is updated each month. Each month I create a new tab as JAN07,
FEB07, and so forth; but when I reach to July, Excel closes itself without
saving my document. One thing that got my attention was when an unknown file
"AA960000" appeared after Excel closed, and another "DB525100" also appeared
after I tried to create the tab again.

Why is this happening and how can it be fixed?

Last year happened the same thing. I worked around it by creating another
file with the first six months and another with the other six months. I don't
want to repeat it again each year.

Your support will be greatly appreciated.
--
A.Oz