Comment 4 for bug 563895

I believe I have the same issue although I had hard locked before the reboot and thus interpreted my boot failure as "needing to reinstall the bootloader" and nothing to do with the snapshot I had made earlier. My specific filesystem is full root + boot LVM ext3. The reason I mention that specifically as I have not tested if this issue also persists with a seperate /boot.

I basically couldn't grub to (re)install and the experienced symptoms described here -> https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/528670

I finally found out that while a snapshot of root was active there was an extra "/dev/mapper/lvgname-lvname-real" device. The key part being "real" here I suppose. I'm pretty new to LVM, but my impression was that with whatever manipulation was going on for copy on write functionality, it could be causing grub to get confused. With a snapshot active Blkid output would now show 2 devices with the exact same UUID.

The moment I killed the snapshot, deleted device.map and ran nothing more than `grub-install /dev/sda`, it completed normally, generated grub.cfg entries loading all the proper modules (raid mdraid lvm ext2) as well as populating a proper /boot/grub/core.img.