Wubi doesn't boot after upgrade

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http://askubuntu.com – I had Wubi with Ubuntu 10.04. I just upgraded it to 12.04, using the update manager. After the upgrade finished, I rebooted, but now, when I select "Ubuntu" from the boot menu, I get a command-line prompt and cannot continue. When I write "boot" in the prompt, I get "No kernel loaded"... Please help, I have important files in my Wubi... (HowTos)