Você precisa reinstalar o grub, pois o bootrec somente restaura o carregador para o Windows. A documentação sobre como lidar com o grub é aqui .
Um resumo: Usando o CD do Ubuntu (recomendado)
A maneira gráfica
Insert your Ubuntu CD, reboot your computer and set it to boot from CD in the BIOS and boot into a live session. You can also use a LiveUSB if you have created one in the past.
Install and run Boot-Repair
Click "Recommended Repair".
Now reboot your system. The usual GRUB boot menu should appear. If it does not, hold Left Shift while booting. You will be able to choose between Ubuntu and Windows.