cannot boot from usb and grub! ubuntu 12.10

cannot boot from usb and grub! ubuntu 12.10

I have an HP ProBook 5330m with SSD, without CD, and Windows 7. I also
installed ubuntu 12.10 and have been dual booting for many months now.
Something went wrong and now I can't boot my laptop at all!
The error message is
error: invalid arch independent ELF magic.
grub rescue>
Another problem is that I cannot boot from USB! I tried to create usb
startup disks - ubuntu live CD, supergrub, ... but when I configure the
USB as first boot sequence, I get the error:
Remove disks or other media.
Press any key to restart
So, I'm really stuck. Any suggestions? How can I recover my system with
the grub rescue shell?