Why is this formula returning "#Name?"?

Hi,

I'm using the attached formula across 30+ rows on a number of
worksheets in a number of workbooks. On every worksheet the formula
returns #Name? in Row 17, but returns the correct value everywhere
else. If I open the linked files instead of updating the links the
correct value is returned in Row 17 as well. This is obviously time
consuming and annoying. Can anyone help?

=+IF(('http://mysite.xxxfoods.com.au/personal/rsutherl/NSW_C8/Shared
%20Documents/[2_Comm_NSW_C8_09.xls]Summary'!D16)="","0",('http://
mysite.xxxfoods.com.au/personal/rsutherl/NSW_C8/Shared%20Documents/
[2_Comm_NSW_C8_09.xls]Summary'!D16))

Thanks in advance,

Rohan