My scans never stop running

After the recent upgrade I no longer have the option to just scan my HD. Whenever I initiate a scan and select my Mac HD it will scan it then begin to scan my backup drive and runs for hours, never reaching an end. I used to be able to just scan the Mac HD but now when I select it I get the same endless scan. The scan option changed and I am not sure how to accomplish this. Any ideas?

forum section for Mac is found here. http://forum.avast.com/index.php?board=5.0