Re: Natty works fine off USB stick, but freezes when I try to install
/dev/sda2 (the partition that caused GParted to fail) uses Btrfs, which is brand-new and not yet ready for widespread use. My hunch is that your version of GParted simply lacks Btrfs support, or perhaps that support is still buggy. There's very little point to a 3.26 GiB Btrfs partition, BTW; that's too small for a full Ubuntu installation, and Btrfs's most important advantages over other filesysstems are in handling larger files and partitions.
If I've suggested a solution to a problem and you're not the original poster, do not try my solution! Problems can seem similar but be different, and a good solution to one problem can make another worse. Post a new thread with your problem details.