Are you saying scour.com is 1 of sites you are directed to or is this the name of the virus. My security shield fake AV used to redirect to this site do you have it in you program list?
I would run stinger followed by getsusp and malwarebytes. Stinger needs a new download daily to update getsusp needs your email addy to be placed in preferences so Mcafee can contact you and malwarebytes use only teh free version do not trial the full version it will clash with mcafee.
These programs here
Re why Mcafee cannot detect it depends on what placed it there fake AVs are hard for the mainline AVs to detect. See what the above does for you.
Of course you tried a restore point prior to this intrusion?