I recommend downloading the official removal tool, because uninstalling the application using the classical way won't remove other files that are probably corrupted. Access the official website of AVG and download the Remover tools. Launch them and fully clean the computer of AVG then re-install it.
Download tools: http://www.avg.com/us-en/utilities
After this procedure, reboot the computer, re-install the application again and it should work.
Note: Avoid using 2 security solutions at the same time.