Ask a question mod errors

Hi all, on my site www.themotorcyclemarket.com
Whenever I add an 'ask a question' mod it doesnt work, I cant log in and comes up with an error code and the product crashes on the site.
Tried a different one and now it works fine expect when you click on the ask a queston tab it comes up with an error message at the top, so it still works but looks unprofessional, any ideas?
Error: http://themotorcyclemarket.com/index.ph ... duct_id=51
Thanks, Grant

All sorted, for future reference the only one I found that works is this one:
http://www.opencart.com/index.php?route ... _license=0

I'm on version 1.5.6.4