Order click redirects to administrator URL

-- url of the page with the problem -- : www.dyssekildeyoga.dk/
-- HikaShop version -- : 2.6.0
-- Joomla version -- : 2.5.28
-- PHP version -- : 5.6.15
-- Browser(s) name and version -- : Any
-- Error-message(debug-mod must be tuned on) -- : None

Hi there

We have created several products in our shop. Both physical and virtual goods (downloadable MP3's and videos). Suddenly we have a customer who experiense that upon clicking on the MP3 link in the order, she is redirected to the administrator login URL. I have no idea why?? I would expect it to be ACL or usergroup related (after payment), but I have compared to other products and cannot see any difference.

PS: The only mishap I can come up with, is that initially there was a restriction on no. of downloads per order. Set to 50, but now set to 1000. I believe that when I have set it to 1000, it will likewise work on previous orders and not just future.