404 error with the category module created

Hello,
I have used the tutorial on creating a category module for hiklashop.
But as stated in the tutorial:

If that option is not setup automatically or manually, you will get 404 errors on Joomla 1.6+ if the SEF is activated in the configuration of Joomla when you click on the categories link of your module.

How do I use joomla SEF and get rid of the 404 error page?
Thanks,
Charlie