after installing mobilehotspot i restarted my phone, it didnt work went black screen doesnt work at all so i thought of reflashing it so i connected n900 to usb while U is pressed nothing happens doesnt got to bot mod ... any ideas on how i can reflash it or fix this?;'(

PS: i left my n900 connected to the pc the nokia screen comes up after like 10min for 1min and then goes all black again

thanks in advance