A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Certain formulas simply don't work when the linked file is not open. What exactly would you prefer happen when those formulas can't be updated? We can't display the value that was previously calculated, so you kind of have the choice of not updating the links and preserving the previous value, or handling the error in some other way such as wrapping your problem formulas in the Excel 2007/2010 IFERROR() function, like
=IFERROR(SUMIF(....),0)
which would return 0 when the SUMIF(...) formula generates an error.
You might go into [File] --> Options --> Advanced and scroll down to the When calculating this workbook: section and making sure that the "Update links to other documents" and "Save external link values" are both checked. Then you might see how things work for you if you clear the first one (Update...) but that may force you to manually update those values. Not sure ... haven't played with it all much and am not sure of how things actually work with various combinations of those two option settings.