avast free

Hello, I installed the avast free today on my laptop (windows 7). When I try to do a quick scan it says it is scanning but stays on 0%
When I try to o a full scan I get this message :
there are no more endpoints available from the endpoint mapper
Please help

What version of Avast?
Any other Security Software installed?
Any other Anti Virus software installed prior to Avast. If so, how was it removed?