Hi,
I don't really know why but your website includes jquery, then mootools and then hikashop.
When hikashop asked for the inclusion of "jquery-ui", it seems that it does not work properly so the script execution stops.
It means that the uploader in HikaMarket 1.4.4 based on jquery (which will change with HikaMarket 1.5 with a new standalone one) does not load properly.
So your page is falling back on the classical upload system which require a popup to upload a file.
But the popup that you use in HikaShop is the "bootstrap" one ; which is not compatible with your template.
You can change the popup system to "mootools" in your HikaShop configuration (tab display, option "popup mode").
You can also install the extension "jquery easy" for your joomla website in order to fix the issues between jquery / mootools and jquery-ui.
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.