i also had this error, my dell xps laptop had win8 on it already and 2 disks (750GB + 32GB ssd).
because the installer always failed on the 'partitioning' page, i opened gparted to see if i could edit them manually.
note that i *only*
wanted to install mint -- i *wiped*
the windows install, and i *did not check*
whether windows was still bootable after making the following changes!
Gparted opened with an error dialogue saying "The backup GPT table is not at the end of the disk, as it should be. This might mean that another operating system believes the disk is smaller. Fix, by moving the backup to the end (and removing the old backup)?". After choosing 'fix' there was a further question about adjusting to use the full disk size, which i also fixed.
This happened twice, i guess once for each disk?
After this i restarted the installer, and everything worked as expected.
i found this bug which may be related -- looks like newer windows do something odd with partition tables?https://bugs.launchpad.net/ubuntu/+bug/777056