Problem with not showing text or can't run.

Okay, my bro had this problem for a while when he can't download anything from the internet, can't play youtube videos, can't use Facebook because nothing will show, pop ups for logging into game will be blank and his McAfee won't show anything either and etc...
I got AVG Tune Up to clean everything such as reg, files on the internet, and fix corrupted shortcuts etc.
Is there a solution for this? :confused: