Thanks !

I already tried typing run noloboot ( dont know why but, it worked kind of ! ) I left n900 home and after I came home i tried to put USB cabel and pressed down the U key, then it went to flashing mode. I didnt have maemo flasher open and i had to read again the command for flashing the kernel and i just pressed the U key all the time cause i was afraid that N900 wont go again to flashing mode if i released the button

I managed to flash the kernel and i booted my N900 but nothing happened and now i cant get it to flashing mode anymore so the problem is back again.

This time it lightens the screen and if i try to boot it from the power-button it starts up but thats it. Only NOKIA text appears on the screen but not the USB icon. Should I just wait with the U button for a long time could that help?