As I have posted earlier, Ubuntu upgrade broke my installation and I had to reinstall everything from scratch. And guess what, it happened again! This time, I've some important files in the filesystem. And since it happened the second time, it can no longer be said as an accident. Something breaks during the upgrade and it must solved or at least mitigated the next time. And apparently, I'm not the only one affected and there are at least three bugs reported already.
Meanwhile, a solution/workaround has been posted at ubuntu forum. Click here to view the thread. If you are too lazy to open yet another window/tab, here's what fixed my Ubuntu install.
You have Wubi installed and are able to boot Windows normally.
However, attempting to boot Ubuntu leads to a number of possible failures including, but not limited to, the following:
computer reboots without user interaction, a black screen with or without any error messages, loadfont errors, file not found errors, and the like.
These issues affect the following versions: 10.04, 10.04.1, and 10.10
The solutions for each version are somewhat different and will be noted next to the relevant solution.
Solution #1 (10.04):
If it is a 10.04 install, the fix is to boot an Ubuntu LiveCD/USB, loop mount the wubi root.disk and manually edit the grub.cfg file.
Here's the steps
sudo mkdir /media/win
sudo mount /dev/sda1 /media/win
sudo mount -o loop /media/win/ubuntu/disks/root.disk /mnt
sudo cp /mnt/boot/grub/grub.cfg /mnt/boot/grub/grub.cfg.copy
sudo chmod +w /mnt/boot/grub/grub.cfg
gksu gedit /mnt/boot/grub/grub.cfg
Note, this is only applicable for WUBI.