The thing is when i activate the theme index.php process starts to multiple until it crashes the server, causing extreme load very quick. But the theme worked a long time without this problems, and i didn't change any code recently.

Another interesting thing is i have installed another site on same server and when i do performance benchmark using the ab command it gives me totally different results for sites. The problematic one is doing only 0,3 requests per second and other site over 200 requests per second, how is this possible?