fail to add in catagories

i add a product in specific catagory i want. i also tick the white box before i Ok, but it cannot add to the catagary i want.
one thing i found that , at the left bottom corner , a message also appear, 'done, but with error page'
do you have any ideal what happen.

This was a bug present in older version of HikaShop with Internet Explorer. If you update to the latest version, the problem should be fixed