I had this on a couple of occasions. May not be the same problem, but I found it was due to peripherals I had plugged in to USB ports etc..
Unplug everything "hanging on" and try another installation.
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.