Error 500 - When try to uplad language

Hi All.

I am new user of this script. And i see lot of "BUG" posts but lot of them solved, i hope i will be same case.

stanovi.hr worked on first install, everything prepared befare, all mods and etc.

Only problem which we have is with ADD LANGUAGE button, it scrols down those Input boxes, we write ISO , name. Copy from english... But progress rotating for 3 days, nothing happens, tried several times.

When i try to Import lanugage, i choose file, and after clicking upload i got ERROR 500


Checked file intergrity under admin folder, everything seems ok. But we cant get it work.

Php 5.4, apache 2.0