Try just switching your Modem of for 20 seconds turn it back on and wait for two minutes before you commence.Or try Control Panel, Administration Tools. Scroll down to DNS Client and set it to automatic..Or control panel.Network connections. right click Local area connection and press repair, See if any problems appear.Or speed test, This will start as soon as you open it, click here
Connection a bit slow for 4mb you would expect about 3555kbps at least but its not to bad.You are not connected through a Router are you. Like handy4x said it could be your Firewall,What one do you use.