Links to files not working when source files closed.

I have a customer with a set of rather convoluted mish-mash of spreadsheets,
basically running an entire company. One spreadsheet (SSa) has a number
of links to 4 others (SSb,c,d). Everything works as expected if SSb,c,d are
open, & then SSa is opened, but if SSa is opened before SSb,c & d, cells in
SSa display #VALUE!. I have tried the same set of files on several
machines, running Excel 2000,XP & 2003, all act in the same manner. I have
tried to recreate the problem with a set of files linked in a similar way,
but in any case, the links were able to access data in closed files without
problem.

Any pointers on how to troubleshoot this problem would be greatly
appreciated!

Mal Osborne
MCSE MVP (not excel) Mensa