Not all links are sef

uglyfashionmedia.com/component/k2/item/3...si.html#.TuibLPI6byU

This is one of my links, it seems to be just an ordinary component/k2 item.

Menu links seem to work ok, and I'm sure that these links used to have the category name rather than the item name but it seems not to.

Have I set something up wrong?

Thanks for your help

Having looked at your FAQ I understand his could be an issue whereby I need to put all of my items into a menu.

1. this is quite long winded... or have I got the wrong end of the stick?
2. In order to shorten this process... could I simply add a K2 item to the menu which covers all categories? 

First things first: have you uploaded SEF Advance extension for K2 (sef_ext.php)?

I have indeed.  It seem to work some of the time...  but not for this particular item.

Would it be anything to do with the category?  I have uploaded these particular items to a menu (which is not published to an existing module position)