Hi,
The thread have almost more than 2 years. So I am not sure that what is written before will have the same impact today.
But like for all support post, some precious information are required if you want us to help you.
HikaShop version number
Link to your website
Precise information of the problem (like the url which give you a 404 page with SEF activated).
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.