at the ELPUB workshop the virtual machine did not start on windows machines (it did work on one mac and on my ubuntu).
there was one error re-occuring (5 of 5 machines):

after pressing continue, the boot up process of the ubuntu os (after selecting it), stopped and no commands were executed and listed up. nothing was moving, so the start up process was stuck in the middle. can not really say, if the problem relates to the error message from above.