virtualbox.org

I'm not sure how it happened, but I can't open my virtual machine. Virtual Box shows the drive as inaccessible in the storage settings and gives an error of "Invalid Header". I tried opening the file with VDI Clone, and it gives an error "Source file corrupt - block map contains errors".
I don't know what to look for, but when I opened the VDI in a hes editor the file starts with "<<< Oracle VM VirtualBox Disk Image >>>", so I guess it's the right file.