Hello Rhythme: How long does it run at 40-60%. What other security software do you have installed ie: Firewall, Anti Malware etc. Which version of Avast do you have installed now?
When you realizes the issue did you try a Repair of Avast? Go to Control Panel then Add and Remove Programs and choose Avast, then Change/Remove and scroll down and Click ‘Repair’. When finishe reboot computer.
Sometimes there can be a file corrupted.