For anyone seeing this bug - I found that if you use the on-screen keyboard (from the 'Tools' menu in KVM) you can alt-tab to the various different screens listed at the bottom. On one of the screens it switched to I notcied that a couple of ^C characters were at the bottom of the screen, I deleted these and pressed return and a minute or so later the installation completed.
Basically it seemed like the installation had interrupted itself somehow.
