The installation has been stuck here for about 9 hours now. Also, applications and files won't open, making the computer unusable. Would canceling the upgrade be a bad idea at this point?
I have the same issue. Look up on this blog: http://blog.mattrudge.net/2012/04/26/ubuntu-12-04-lts-upgrade-first-looks
You need to click "terminal" below in your upgrade window and do some action it is waiting for