cannot compile prepared_statement.cpp

[tizio incognito]

Hello to everybody
I'm having problems trying to compile the example prepared_statement.cpp included in the c++ connector sources with Visual Studio 2010, particularly, I get the following errors on this statement:

std::auto_ptr< sql::PreparedStatement > prep_stmt(con->prepareStatement("DROP TABLE IF EXISTS test"));
prep_stmt->execute();

The compiler says that "pointer (prep_stmt) to an incomplete class type is not allowed"

Any clue?
Thanks in advance.