no longer can calculate cells Excel 2003

Hi all,

New here so not sure I've posted in the correct group.

Have a user who is no longer able to add or do any type of calculation on any group of cells unless she opens a new spreadsheet in the background.

The spreadsheet was created by her.

Any ideas.
thanks

thanks

The sum of any amount of cells always =zero, unless a second blank spreadsheet is opened where the saum of the cells then is correct.

very weird

Kata