Norton (aka Symantec) can be a complex and interactive set of protection programs. Sometimes they'll update one part of that set, but not have the correspoonding updates for the other parts, so you get a program (mIRC for example) being alllowed under, 3 out of 5 parts (again example only) of Norton, that still means that those other 2 parts are going to recognize that mIRC is being used, but they don't have anything in them (yet) to tell them that it's OK.
That's as simplistic as I was able to make the official response from Symantec when I queried them about the same thing. Their response is nearly 10 pages in length.
