Comment 21 for bug 441941

On my HP dc5800 microtower I got same problem.
Continuing on JohnL messages: Just downgrading grub also resulted in some 'hybrid' for me. Cleaning up a bit more brought me to the 'oldfashioned' grub. So far (a few reboots) no problem anymore. What I did:

sudo apt-get purge grub-pc
sudo rm /boot/grub/*
sudo apt-get install grub
sudo update-grub
sudo grub-install /dev/sda (replace sda with your boot device!)

Add a section in /boot/grub/menu.lst:
title Windows XP
root (hd0,0)
makeactive
chainloader +1