Aha! Sorted! AFM is quite right, both about the empty NZBs and the comments being the place to look. To save you the bother here is the method I found has worked.
I went to
http://www.securitykiss.com/ and downloaded the free software. Then I connected Opera in turbo mode and downloaded the NZB file to my desktop.
I then disconnected the SecurityKiss thing and clicked on the NZB to open it in Grabit and it seems business as usual.
Worked for me anyway. Ta.
