filament curl up in the j-head

hi!

I have a problem. When i print, the filament curl up in the j-head or the feed tub.
I dont know witch factor cursing this behavior. i see three diferent factor that can course this. But i dont know witch one. I tried different way to solve this problem but none of them did solve the problem.
the temperature: i tried different temperature but dont seems to mater
feeding speed: i tried to change the speed with some success but then the filament get choppy.
hotend hight: i tried higher the printer head. but the filament get choppy.

any ides what can course this behavior or witch factor that could course this.

here is a link how its looks. http://www.ehel.se/3d_jam.jpg

thanks for help.