[bass booster]

As stupid as this sounds, that last time I had this error, I redownloaded the ISO and it worked lol.

Try that and let us know

[TheGrayAviator]

1) Re-create your virtual machine
2) Download that .ISO file again.

[Flacko.]

Check to see if the options are enabled that you are suppose to in BIOS.
Maybe the VM itself got corrupted, I don't know.. it's never happened to me. :(