In rare cases, some software/drivers/programs claiming to "optimize" or "enhance" your network connection can actually cause more problems. Try uninstalling any extra software / drivers related to your network card other than the core driver that needs to be installed for Windows. Avoid using any "optimization" or "tweak" programs. Certain network cards come with custom configuration utilities (most notably Killer Networks) that can cause issues and need to be removed for a drivers only install.