Can;t get AVAST to work

I downloaded the free home version and it loads and there are no errors, but I cannot get the virus guard to work. There is always a little red mark on the ball in the startup bottom right hand corner and it won’t go away. Not sure why. Any ideas?

Red Circle on avast icon, http://www.avast.com/eng/faq-avast-4-home-professional.html, see if this FAQ offers any useful pointers.

Are you also getting any error messages, like “AAVM subsytem detected and RPC error” if so see, http://www.avast.com/eng/faq-other-questions.html#idt_1539.

This is also often associated with an other anti-virus program. Have (or did) you have another AV installed in this system, if so what and how did you get rid of it ?