Help!

I've been creating worksheets that reference other workbooks and all of a
sudden, when I open the worksheet I've been working on after the dialog box
comes up saying, "This workbook contains links to other data sources" and I
click "Update" then I get the "Unable to read file" I click OK, then I get
the "This workbook contains one or more links that cannot be updated" and I
click "Continue"

So, I have re-booted, and then reinstalled Office (according to the forum
instructions) but now I am at a loss.

Interestingly, when I go to the other workbooks that Excel is "unable to
read" and I go to Tools, Share Workbook... and check the box the files then
can be opened by my worksheet. And, if I go back and uncheck the box, My
worksheet can still access the workbook. However, this isn't an option, I
need automation.

Any help or ideas would be greatly appreciated,
TIA,
Greg