ldap_memfree crashes on x64

Hello,

Here is my source code:

LDAP *ld;
....
char *errorString = NULL;
int err = ldap_get_option(ld, LDAP_OPT_ERROR_STRING, &errorString);
ldap_memfree(errorString);

It works fine on XP/Vista 32bit, but it crashes on Vista x64.

How to solve this issue ?

Thank you