Well then, I was right after all; BitDefender was at fault. I finally made up my mind and decided to uninstall bitDefender 2013. So I ran the BitDefender Uninstall tool I used to uninstall bitDefender 2012. It seemed to have gone through the process ok, then as expected asked for a restart to complete uninstallation. I didn't realize that only the uninstall tool specifically made for bitDefender 2013 could uninstall it. So, after restart bitDefender 2013 was still present and running perfectly. However, the difference now was that visual studio had no problem debugging my applications neither my browsers any problem loading my Silverlight apps either locally or externally.
Weird? Believe it.