My update manager told me that it has not checked for updates in the past 18 days, so I clicked the "check" button. It works just fine until a certain point where it says "Downloading release". The loading bar moves across the screen for a while on that message, then it just stops and says to check my Internet connection. I am fairly certain that my Internet is fine, as I can do anything else that I have tried, including installing software over the Internet.

I clicked on "Details" and this is what turned up: Log