Avast always detect alware

I use Avast free 2014.
When I open main UI of Avast is appeared this popup:

http://pik.vn/20148417f54c-22fb-4667-9bba-0075d8d2b514.jpeg

And I open web browser as FireFox, I click any link is always popup about “URL: Mal google-analytics.com/analytics”, always.
I used Malwarebytes Anti-Malware scan but can’t solve. Anyone can help me >.<

Sorry for my English.

https://forum.avast.com/index.php?topic=53253.0