If you used the 'advanced/manual' way of partitioning and did not let the installer to recreate everything, you have to make sure that you have created a uefi partition larger than 200Mb and after that you specified the grubloader to be installed on /dev/sda (automatically is set to /dev/sdb for a reason i do not really understand).
What i did to fix this was to create the uefi partition using gparted and after that follow this instructions to reinstall grub: http://www.howopensource.com/2012/05...4-live-cd-usb/
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