Gparted funkiness - won't recognize 1TB, full-hdd /home partition, but recognizes ext4 and /home label

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http://askubuntu.com – I have a 1TB SATA hard disk from my old desktop, and the entire thing is an ext4 /home partition (/, /boot, and swap were all on another hdd). It is now in a USB2 enclosure and I want to use it to back up my current laptop /home. To do this I need to shrink the /home partition on the 1TB backup drive. It only uses about 500GB so that shouldn't be a problem, I'll start the laptop with an Ubuntu live USB, plug in the 1TB drive, and use Gparted to shrink the 1TB /home partition to ~500GB. Then I can create a second partition in the newly freed space, and cp -ax my laptop's /home over to it. (HowTos)