Norton 2010 failed to delete cookies?

I ran a quick scan today like I do every time I get off the net and noticed I had several cookies that NIS 2010 said it had dealt with...

but I noticed some were marked as "partially"...and when I clicked to find out more info it turned out that over half failed to delete.

 

So I ran a scan again and this time it said there were no cookies or security threats...

 

well what happened to the ones that it failed to delete?

 

And why is it they failed to delete?