I could not recover the grub, but I found the problem.
In some machines, the Ubuntu 10.10 LiveCD has a bug. The problem is that the regular ISO still has the error, though a bug fix is available. But the MinimalCD is clean and works fine.
I did this process and managed to install Ubuntu Desktop 10.10 32bit smoothly. It is also valid for other versions.
If you're using a regular ISO, and you can not continue the boot process, you can see the bug as follows:
When the boot process stops or freezes, you need to press "F6" and "Esc". Then you can see one or both of these messages:
"GLib-WARNING **: getpwuid_r(): failed
due to unknown user id (0)"
"Kernel panic - not syncing: Attempted
to kill init"
Finally, the solution:
To solve this problem, you can install Ubuntu from a MinimalCD (simply choose which version you want):
After booting the CD, I chose the standard install, and near the end, I chose the version I wanted. In this particular case, Ubuntu Desktop 32bit 10.10.
For more details: