I have the following suggestion for the wizard interface: I thought it would be great to keep the user from proceeding to the next page if the user has not provided the required inputs yet. This could be done by simply disabling the next button.
thanks for your suggestion. Actually, this was already supposed to be the case, and I am quite sure that it worked some time in the past. But, in fact, it is currently broken, and apparently it has been broken for a long time, already.
Now fixed in our development version (http://p.sf.net/rkward/svn).