Random crashes when using WWW class

I use a lot WWW class for http request with my server and it seems it causes the game to terminate itself sometimes. My game is rejected because of that and I don't know what is wrong cause this code works very well on any other platforms, iOS, android and windows phone. There must be something in http request handling that causes the crash but the console output isn't really helpfull, I got things like this when it crashes:


[21.854279] HTTP status Code is 200
[21.854792] HTTP start transfer...

Random crashes when using WWW class