I am annoyed by pop-ups coming on frequently saying " Avast network shield has blocked a harmful site"....
this indicate that you are infected......something is trying to phone home

follow guide and attach the requested logs (not copy and paste) http://forum.avast.com/index.php?topic=53253.0

run in order listed
AdwCleaner / Malwarebytes / OTL / aswMBR

when done removal experts will be notified and check the logs for infections…

if trouble running any of the Tools, try run from safe mode…