I prefer (out of superstition, I guess...) installing updates through a wired connection, and so I turn off my laptop's WIFI every time I'm about to give the Update Manager the go-ahead. A bit tedious. Is there a way to set the Manager's preferences so that it chooses the wired connection by default?
My understanding is that when you are connected to a wired and a wireless connection at the same time, your computer will choose the wired ethernet connection. To test that theory on your laptop, plug in an ethernet cable and then go to the network manager applet in the top bar. Choose connection information from the menu and it should say you are connected to wired ethernet at the appropriate speed.