One of the users I support gets the following message when he opens some
.xls files

Timer:  Error:  91  Object variable or With block variable not set.

There are two scenarios where this happens.  In both cases the error message
appears above another message box.  After clicking on the error box it
continues to reappear until you quickly click the background message box.  I
searched the MS Knowledge base and some newsgroups such as this one, but all
hits involved macros or custom code.  There are no macros or custom code
associated with any of these spreadsheets.

Case 1:  The spreadsheet has cell values that are linked to other
spreadsheets.  The background message asks if you want to update the cells.
Case 2:  The spreadsheet is configured to recommend opening in READONLY
mode.  The background message is regarding that.

This behavior is confined to one machine running Excel 2003 as part of
Office 2003 on Windows XP.  I believe all patches and updates are current.

Thanks in advance for any help or insight toward fixing this problem.

Kent