You better uninstall the realtek high def and make sure to clear cookies and begin installing the latest version of it. I had a hard time in realtek before when I updated my OS but it's solved now.

Probably you need to upgrade your browser to the latest version. Or, could be your flash why not upgrade it too. I occasionally experienced such thing where uploading photos encounter some errors,...

I don't think it is advisable to a 3rd party antivirus. You may want to always update the Windwos Defender and you're fine. Just wondering why you may want to install another antivirus. Are you not...