installer can't change partition sizes

[Graham Menhennitt]

I don't know if this is my mistake or a bug, but I can't change
partition sizes when installing 10.1 RC3. This is both in the Guided and
Manual partitioning. I'm doing this from memory so please forgive me if
I get it wrong.

I start the installer, select the keymap, and enter the hostname. I say
that I want to use the whole disk for FreeBSD. It then gives the me the
choice of partitioning methods: Guided, Manual, Shell, or ZFS on root. I
choose Guided and it automatically defines 3 partitions -boot, -ufs, and
-swap with various sizes. I'd like to have a separate /usr partition so
I try to change the size of the -ufs partition. But I can't get the
cursor to move into the size field. It moves between the Type field and
the Ok, Options, and Cancel buttons. But it won't move to the Size
field. I've tried arrows, tabs, enter. If I delete a partition and
create a new one, the same things happens - the partition is made to
take up the remainder of the disk space and I can't change it.

The same thing happens in Manual mode.

Am I doing something wrong?

Thanks,
    Graham