Thanks for your reply, I appreciate it! By the way I am using OCS 18.104.22.168. I am going to test what was said in the thread you have pointed. However, I think my problem is different such that I don't get any error messages. I try to log in using the admin account while the Turkish lang is selected in the language combo and OCS just reloads the login page without any error messages!
While writing this message I wanted to check another language and installed German language support (provided with the OCS package) and it logs me in without any problem!
By the way is there a translation plugin for OCS like there is one in OJS?
And finally, before you ask I WILL submit the translated locale files [tr_TR] once we finish the work...