Another data point from one of my interns: he noticed on a new machine that IE had never been opened, and had it’s security settings accepted. Once he did that, then went back to SketchUp, he was able to get online and log in.
@mac7595 hits the point: it sucks if you’re one of these < 1% people that runs into issues like this, and we will engineer these issues out of the product in the long term, but in the short term, it’d be best if you tried the workarounds and data points we’re trying to help you with, and reported back on success or failure. I’ve yet to be stumped by a machine, but I can’t go around trying the umpteen fixes on all 30 million SketchUp users.