We are experiencing lockups when loading certain parts of our website like the Add On Store. If you encounter this problem we recommend trying an alternate browser to see if that resolves the issue for you, we are currently experiencing the least issues with Firefox.
Update: The issue happened only on Chrome, as far as we can tell, and it is due to Chrome not being able to handle more than just a few CSS animations (in this case spinning a .png file) without sometimes deadlocking. We removed those for now to work around this Chrome bug.