How do I enable automatic updates of links between spreadsheets?
 

I have a series of spreadsheets that were created in Excel 2003 where data is
shared between the spreadsheets and they are linked together. Now that I
have upgraded to Excel 2007 and saved the spreadsheets as xlsx, I receive a
message "Security Warning Automated updates of links has been disabled." and
the information is no longer being updated between the spreadsheets as there
were before the upgrade. Even if I select the option to Enable the content,
they next time I open the spreadsheets the message reappears and I am unable
to update the information. I tried to recreate the scenario using
spreadsheets created in 2007 and the message does not appear. I can not
afford to recreate these spreadsheets so I need to find a way to fix this.
Does anyone have any thoughts?