Result set names don't match

Cognos 8 Business Intelligence Report Studio
1

I created this filter:
cast([Phonak Sales].[TicketExpert].[OpenDate],date) > ‘2013-05-31’

I receive the error:
CCL_ASSERT_NAMED(rResultSetName == rsCurrentResultSetName, “Result set names don’t match.”)

The backend is SQLServer 2005 and the field is defined in SQL as DateTime.

I get the same error if I use:
[Phonak Sales].[TicketExpert].[OpenDate] > cast(‘2013-05-31’,date)

Any help would be appreciated.

Thanks,
Ken