Pivot Tables break when an Excel spreadsheet is opened from a Sharepoint site

I posted an Excel spreadsheet to a document library in our Sharepoint 2003 site.  When I open it from there, all of the Pivot Table source data is ‘broken’.  Rather than using the named range ‘[rangename]’ that I had given when I set up the Pivot Table, it now points to https://[servername]/[sitename]/[filename]’![rangename] which it then can’t resolve.

Has anyone else run into this problem?  I’ve done some Web searches, but can’t find any reference to it.