A fairly big Moodle provider had a power outage earlier today, which had the same effect on our Moodle installation.
Here was their original report:
We are currently experiencing an issue
with power in our data centre which is affecting our moodle customers. We are
aware and engineers are onsite. We will keep you up to date with progress via
our twitter feed here and
It may be that your university is using the same supplier?
Ours has just gone back up again, so stay tuned. Should be resolved soon.