Yep I'm getting the same, probably too many people trying to access at the same time. You'd think they'd of been prepared, I mean it's not the first time they've allowed you to apply online for accommodation surely.
I get a message to say that there is a problem with the server. What they should have done, in my opinion, is to say that the portal will open sometime between the 16th and 18th of May, that would have staggered it a bit.
They should've just told us the day and not the time, then there wouldn't be this problem. My sister applied for her accommodation on Monday and she got straight on and managed to book without any of these problems.