Norton ID Safe on iPad Mini closes down on Facebook

I have Norton ID Safe on my iPad Mini and it works perfectly, except when I login to Facebook. It works for about 20 seconds and then closes down. Then I have to sign in to the ID Safe again. I have deleted the ID Safe App and reinstalled it but it is no different. I have IOS 7 on my iPad Mini. Facebook is the only website that it doesn't keep me logged in. Hoping somebody can help.