Sounds like you need to uninstall avast again and run the removal tool http://www.avast.com/uninstall-utility to clear out leftovers, after removing it can help to run a search through your system for Avast entries and run a cleaning tool such as Ccleaner then reinstall avast.
Threatfire isnt recomended nowdays and can have some conflicts with avast, the better tools to run these days are Malwarebytes and Superantispyware.