In the 4-18-03 Stable release, DB.php contains these defs:

define("DB_ERROR_CONNECT_FAILED",     -24);
define("DB_ERROR_EXTENSION_NOT_FOUND",-25);
define("DB_ERROR_NOSUCHDB",           -25);
define("DB_ERROR_ACCESS_VIOLATION",   -26);

Note that two of them have the same error number.

The defs should be:

define("DB_ERROR_CONNECT_FAILED",     -24);
define("DB_ERROR_EXTENSION_NOT_FOUND",-25);
define("DB_ERROR_NOSUCHDB",           -26);
define("DB_ERROR_ACCESS_VIOLATION",   -27);