Excel links to other workbooks

Hi,

I have a spreadsheet which consists of a lot of links to other workbooks by using formulas like this =[AA.xls]Sheet 1!A1.

There's one workbook in particular doesn't give its appropriate values in the master spreadsheet, instead they all show zeros. I've checked the cell formatting - nothing gone wrong. But strangely, when I have both the master and the problematic workbook open, the values come back.

I really need to know what the problem is here since it's not really efficient having both workbooks operating at the same time and it just looks unprofessional during client meeting...

Would be very much appreciated if someone could come up with a solution.

Thanks!
Sammie