Don't do the Avira thing while AVG is still active.
Two resident AntiVirus programs running are a recipe for disaster, especially if your system is already unstable.
Choose one or the other, Avira is better in my opinion, but if you want to scan with an antimalware application and keep your current AntiVirus program I would recommend running Malwarebytes' Anti-Malware instead.http://www.malwarebytes.org/
Download free version, install, update and let it do the quick scan.
I would follow TheViper's advice and upgrade the browser too.