If your TMPDIR environment variable is pointing to a directory that is not world-writable, then the graphical installer will fail to complete installation. To ensure that this situation does not occur, unset your TMPDIR environment variable or set it to a world-writable directory before starting the installer.
This problem also occurs if you specify a directory that is not world-writable with the installer's --tempdir command line option, so you should be sure to specify a world-writable directory.