Peter,

Just a SWAG and probably unrelated, but you may be creating two indexes with the same name but different expression. Fox might be confused by that. I would add a simple check:

if tagno('Title')=0
  index on ...
else
  && index with this tag name is alredy created, you may just use it
endif

>I'm using a simple "INDEX ON UPPER(Title) TAG Title" type of statement. Since I'm indexing a view, I'm not even sure what you'd do to create a "non-structural" index: "INDEX ON UPPER(Title) TAG Title OF [viewname]"? Since views get created dynamically, the whole notion of structural seems obscure.
>
>You might be on to something with Rushmore and the value of "criteria" but for the fact that the problem ONLY occurs when the user has opted to view the grid in some particular sort order (which they do by double-clicking on the column header, the CLICK event of which issues the INDEX command as described above).
>
>We have another application where users are updating and adding records to sorted views all the time without any errors. The only difference there is that the nature and number of the indexes is always the same; it won't vary from user to user. In the application that produces the errors, each user can sort on one or more fields, completely at their choosing and independent of what another user might be doing. We were wondering if, somehow, some of this was getting stored in the DBC and a conflict was arising because the indexes that one user was using on the view were different from those being used by another user.
>
>I'm still scratching my head - thanks for the input.