Hi,
Like kernel64 explains it's a cache problem.
Joomla (or another cache plugin) stored in his cache the page and gives it to the guest users thinking that, all users would required the same cached page.
As we said a lot of times, HikaShop is not compatible with cache systems.
(but GZ compression if compatible with HikaShop)
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.