Issue with Full Scan taking too long.

Just bare with me on this issue, I am doing the best I can to describe what is going on. I just hope this is not too confusing. I posted on another Norton through Xfinity.

I seem to be having an issue with the full system scan. I have two computers one of them takes only thirty minutes to run a full system scan, this one does not have a lot of on-line activity. My computer has been scanning for two hours now. I had to stop the scan manually.I would like to what to do, should I just let the FSS run until it is finished?  This happened today. I never had this problem with the full system scan before.

It first started last week when I ran the FSS and another application popped up waiting to be installed. I minimized the application. I wanted to wait for the FSS to finish up.  It seemed to be taking hours to finish so I stopped the FSS manually. I am not sure if the application may have caused a problem with the FSS. 

When I ran a Quick scan it did not take long for it to run its course. I do not know what to do at this point. I am wondering if it has something to do with too may bookmarks on Firefox and a lot of saved information on Face Book. It seems to be scanning in one area concerning Firefox/Profile. If it is, should I just delete some of the bookmarks?

I am hoping I do not have to uninstall and than reinstall Norton. Comcast provides our security and anti-virus service.  Any information would be well appreciated.