I have an Excel pivot table linked to a SQL Server table. A filter allows
users to select individual months of data, which is grouped by team leader
and team member.

This setup has worked for a number of months until now. When the user
selects 2007/06 from the month filter, the pivot table now returns data from
April.

The underlying data seems fine; the corresponding fields in April's records
are populated with 2007/04 in SQL (they are varchars, with data stored in
yyyy/mm format).

Furthermore, when you drill into the pivot table, that field is populated
with 2007/04 even though 2007/06 is selected in the filter.

Another option has now appeared in the filter list; 2007/062. When this is
selected, June's data is returned.

Have you any ideas why this has happened?

Btw.
1. The problem persists even when the month field is included as a row
header and only 2007/06 is checked.
2. Several team leaders have local copies of the spreadsheet and ALL
experience the same problem.