URL:Mal avast pop-up keeps appearing

[eldorado20]

Every few seconds an avast pop-up keeps appearing, i'm not sure what i did or why it keeps doing it! But please help? It's really annoying...
It says infection: URL:Mal
I've run my avast and malware check but it says there's no problem. Yet it keeps popping up.
Can anyone help?

[DavidR]

This needs further analysis by a malware removal specialist:
Go to this topic http://forum.avast.com/index.php?topic=53253.0 for information on Logs to assist in cleaning malware. Use the information about getting and using the tools and start your own new topic and attach the logs there, not in the LOGS topic.

Please create your new topic, here http://forum.avast.com/index.php?board=4.0 in the viruses and worms forum (click the New topic button at the top of the page see image) and we will try and help you there.