Sorry guys, we’ve just found out what the problem is:
http://sellwire.net/recent-downtime/
While this explains why there are currently problems, it’s actually not quite fixed yet (as stated) and we’ve emailed the developers with a heads up about the remaining issues.
In the meantime, if you’d like, we can manually email you the latest theme versions for you to upgrade manually. Or wait another 1-2 days for all the kinks to be worked out and you should be able to upgrade automatically with ease.