Note: I just re-tried v1.26 and it is working now! Seems this was a false alarm??? v1.26 and v1.27 should be the same and no need to update to 1.27!
v1.26 seems to have a problem with Win8 Install ISOs if a Helper USB drive is used together with a USB HDD - please update to E2B v 1.27 or later!!!
The problem seems to be in the \_ISO\e2b\grub\ENG\RunWin8.g4b batch file, but as far as I can tell it has hardly changed for at least 3 previous versions, so I am not quite sure what the problem was. When I added a few lines to debug it, it just started working again!
v. 1.27 seems to work though, so please update to this new version ASAP.
Sorry for the inconvenience, I am still trying to figure out why it stopped working....