After a great month of smooth running, it happened again. Wubi is a great way to install Ubuntu if you would like to keep your Windows partition intact, but this seems to happen to me a lot. Basically, you install it. It works lovely. You install updates, including a grub update at some point. Then, next time you try to boot into Ubuntu, grub can’t find the menu, and you are left at a grub prompt.

In order to boot into Ubuntu, you will need to enter the following into the grub prompt (press the tab key to auto fill or see which kernel versions are available):

Find/set the kernel image:

Set initrd:

Then boot:

It’s great that you can get back into Ubuntu, but now you will have the same problem every time you boot your computer. In order to fix this, you need to make sure grub is installed correctly. It was for me, but just in case, you can just reinstall it through Synaptic Package Manager (System->Administration->Synaptic Package Manager. Do a search for “grub”). I did this, but I don’t think it was necessary. After that, I simply updated the grub menu.

I’ve booted into Ubuntu several times since this procedure with no problems. Here is another link that was helpful for me.
https://wiki.ubuntu.com/Grub2