Protocol 6.4 -> 7.4 - Mailing list pgsql-odbc

Hi,
I was using ODBC with protocol set as 6.4, but the problem was when an error
occurs: the same code was returned for all kind of errors. After some tests,
I changed to protocol 7.4 and the problem was solved.
My question is: what could have changed with the use of protocol 7.4,
besides the error code? I've already done some tests on the statements, but
I'd like to know what to care for.

Thanks in advance,

Renato.