best practise

Dear all,

I am making some sort of questioning system in which people and answer
different questions (with a limited answer set). These questions can
have comments but I will not directly show people that, think of blog
post with associated comments.
A page displays two or three things: 1) the next question unanswered,
2) the previous question with a tally of the given answers and 3)
possibly the comments on that previous question.
Now I made and URL much like:

But this breaks down if I have a form where people can leave their own
comment and the new comment fails validation. Normally in the
controller I would write; render :action => new_question (or something
like that). But that does not work now because showing comments is
coded in show_comments=true. And I need to show on thesame page the
previous and next question as well.
Am I still making sense?
How would you solve this?

With kind regards,