Using Disk Druid on a system with only one drive (hda in my case):
Click "Add" to add a new partition.
Use ONLY keyboard to fill out the dialog box:
Mount Point: /usr<tab>
Size (Megs): 2048<tab><tab><tab>
Allowable Drives: <space><tab>
(Note how the space bar deselects the only Allowable Drive)
There are currently unallocated partition(s)...
/usr Allocation Succeeded
(Note how the /usr partition shows up in red.)
Highlight /usr and click "Edit" to edit the partition.
Allocation Status: Failed
Failure Reason: Allocation Succeeded
So, we successfully failed. :-) Seriously, I think the bug here is that,
just as you can't deselect the last drive using the mouse, you shouldn't
be able to with the keyboard either.
Fixed in internal build.
Confirmed fixed in Winston Beta-3. A dialog appears if you try to leave the
screen with no drives selected. Thanks!