Sorry, ignore last post. Go to Control Panel>Device manager> Network adaptors. select your adaptor and right click. Try updating the driver first, if that fails then uninstall and reinstall.
Have you tried running a malware check with Malwarebytes, it sometimes picks up trojans that your AV misses.
Edit: You could also try flushing your DNS cache. Open a command prompt and type ipconfig /flushdns
If you are going to do a virus scan or run a malware scan you are best to start your computer in safe mode then run the scans. This will stop anything from running that may interfere with the scans.
See link how to start in safe mode.
Tried the command prompt but says "the requested operation requires elevation"?
Before clicking on the command prompt, high light it with your mouse and right click, select "run as administrator" then run the flush.
Don't just hold the F8 key, you need to keep repeatedly pressing it until the safe mode window appears. If it starts as normal you need to restart it again and repeatedly press the F8 key.
If you can not get into safe mode that way you can go to the Start button and in the search box type msconfig and click on the icon it brings up and go to the Boot tab and tick the box Safe mode.
Once the computer restarts run your scans. After you have completed the scans, bring up the msconfig box again and this time select the "Normal" tab and tick the box "Normal Start Up" and restart your computer.