NULL TEXT value gives 'Requested conversion is not supported'

[Daniel Savstrom]

I have a kind of sparse table that contains eight columns, of which the last five are used interchangeably, the fourth being of type TEXT. The following columns are of type DECIMAL, DATETIME, VARCHAR and BLOB. When querying, the result mostly consists of several rows grouped together, and what I find is that if all the returned rows have the TEXT value set to NULL or an empty string I run into problems.

When using the QueryBrowser everything works, but when querying through OLE DB C++ the IRowset::GetData() method gives me 'Requested conversion is not supported'. The same code is working fine on Jet, SQL Server, SQL Server 2005 Express so this is a fairly well tested module.

If I add anything to the TEXT field in any of the returned rows the code works. It looks as if the column is ignored altogether.

I have the latest MDAC, MyODBC, MySQL and I am fresh out of ideas. Please help.