DB Inbound – Fail to convert resultset to row set

I am using a DB Inbound protocol and using a SQL statement, not a stored procedure. The SQL is a SELECT. The format is SELECT tablename.columnname, tablename.columnname, ……. WHERE tablename.columnname = ‘value’.

The invocation returns “Fail to convert resultset to row set:Index: 123, Size: 123”. What part is the resultset and what part is the row set? I am selecting specific columns, why would that cause some kind of indexing / number-of-items problem?

Peter