Operations error in ldap_search() in PHP

All that has been occurring to me leads me to think this is more a problem with LDAP connection rather than PHP. I might be wrong, of course.

The problem is: I'm configuring a third-party PHP system for my company, and it has a module for logging in from LDAP/AD bases. When I activate this module, I try to log in and I get this:

exception 'Exception' with message ''Warning:
/var/www/html/infra_php/InfraLDAP.php line:345. ldap_search(): Search: Operations error '' in /var/www/html/infra_php/Infra.php:149

Nevertheless, when I refresh the log in page and try to log in again, it works flawlessly. And even sometimes it works at first, straight away. I'm really having a hard time trying to figure how could this happen, how could it stop working so... randomly.

Does anyone have a clue about how could I fix this problem?

Does your search query change depending on a variable? Maybe it's not complete sometimes and other times it is. Can you post part of your code?

Well, I talked to the Network Administrator and he tried to use another user to access the LDAP base. Apparently it worked fine. Don't know if the former user had some restrictions, but now it seems to work. However I'm not sure yet, even with the bunch of tests we did yesterday... But thank you for your readiness in helping me.