My Acer Aspire 5742 runs on Microsoft Windows 7 and Ubuntu 12.10. I installed 12.10 as an upgrade when it came out, and as of today it is not booting. It gets stuck at the purple screen. For a while it would hang there and not show the Ubuntu with the dots until right when it shows the lock screen. I left it to boot for a while and after more than 1 hour it still was showing a blank purple screen. What do I need to do to fix this?