Comment 24 for bug 441941

Okay, after many restarts, I've discovered what caused the corruption.

The program that corrupt the grub (in my case) is "PC Angel" a recover software, more exactly their windows service.

You can disable it by going into Start / Control panel / Administrative tools / Services, search for a service named "PC Angel" and right click it, then click Properties, and select the start type to disabled.

For restore the grub, the only thing you need is to boot into ubuntu and using Synaptic (for example), reinstall grub-pc and grub-common.

I have used the Super Grub Disk (version 2) to launch first into windows for disable PC Angel and then to go into Ubuntu to reinstall grub. If you reinstall grub before disable PC Angel, you MUST run windows in safe mode (F8) for not damage the new grub installation.

I think that PC Angel, can be disabled if you don't need it to do new backup, because you can initiate the restore if you need, and my grub2 detect the rescue partition.