I am having the same problem and found this answer in another discussion
group. When I checked, the "Automatic" option was chosen. I clicked on the
"Calc Sheet" button which changed the option to "Manual" and any errors
appeared on my sheet. I reclicked "Automatic", did a test (corrected the
errors) and everything seems to be fine. I don't know what happened either.

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Make sure Calculations are set to Automatic.

In Excel 2003 or older:
Go to TOOLS Menu
Select "Options"
Go to the Calculations Tab
Check "Automatic"

In Excel 2007:
Go to the FORMULAS Tab on the Ribbon
Click on "Calculation Options"
Select "Automatic"

HTH
Elkar


"StMel" wrote:

I've got a workbook with several sheets in it, but in several of the sheets
calculations are disabled, for instance I can't sum up some values. The
workbook /sheet and/ or cells has no security settings. What could I have
done to achieve this and how do i enable calculations again ?