..I'd first start by resetting both those browsers to their default state..
After that, it would be a good idea to do full system scans following the instructions in the link below. I know you've already done some of the scans but follow the steps to the letter and it should help.
“Expand” the post titled: "Please try this" at the link below:
Hope this helps.
I'm having an issue at the moment with Google Chrome and now Firefox where, sometimes, when in use, the window will start to flicker as though holding down the Fullscreen button (F11). The window flickers between it's normal size and fullscreen.
As of yet, I've found no solution for this issue.
At first I thought it might be a virus or malware and so I scanned my computer with AVG and Malwarebytes Anti-Malware. The latter found 4 issues and fixed them. Before this I also reset my computer and scanned and cleaned the Hardrive, as at the moment I have few programs on it.
However, I am still having the issue. I've found it stops when I press F11 and then I don't usually have it again. But I'd like to find the cause and solve the issue.
Has anyone else had this problem? And does anyone know how I might solve it or what might be causing it?