Links are not updating
 

When I open a worksheet, the purpose of this worksheet is to summarize and
calculate 30 or so other worksheets. Each of the worksheets are linked to
the summary worksheet. Excel does not update the other worksheets. When I
check the status of the links, Excel tells me "Error: Sourse not Found", but
when I click on the "Open Source" button, the file opens, and Excel will
update the worksheet. Once I close the worksheet, the summary worksheet no
longer recognize it. Any ideas of whats going on here? I am using Excel
2003.