Hi,
Please download the latest version of HikaShop (1.1.3) which contains a patch for a Joomla 3.1.1 bug.
We have already submit a request for this bug but for the moment, no solution.
What I can recommend you is to unpublish the plugin "system | debug". At this moment, the token passed by SEF will be read correctly by Joomla.
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.