Clicking on Next before the choice of which disk to install to has rendered, produces this error (btw, the bug report URL is very unfriendly both to type and because it requires a username / password to post):

Traceback (most recent call last):
  File "/usr/lib/python2.4/site-packages/ubiquity/frontend/kde-ui.py", line 536, in on_next_clicked
    self.dbfilter.ok_handler()
  File "/usr/lib/python2.4/site-packages/ubiquity/components/partman.py", line 225, in ok_handler
    elif self.current_question.endswith('automatically_partition'):
AttributeError: 'NoneType' object has no attribute 'endswith'