If it is indeed doing what you describe then you would seem to have
found a bug in Excel, but it is strange that no-one else has previously
reported such a problem.

What version of Excel are you using?
Do you have the latest Service Pack?
What was the formula shown as before you opened the source workbook via
the UNC name?
What was it showing afterwards?

Bill Manville
MVP - Microsoft Excel, Oxford, England
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