Webshop Buy Error

Can anyone have idea how to fix this , after clicking "Buy item" it will go blank..
im using MuCore 1.0.8

http://i109.photobucket.com/albums/n...6/webshop1.jpg

after clicking Buy Item, this picture below appear.
http://i109.photobucket.com/albums/n...6/webshop2.jpg

Try reinstalling mucore.

or use other template