One of the new ones BitCats.net has been knocked offline as well. It could come back up at anytime in theory tho.
Probably a traffic issue. Hit F5 some times * and it'll come
* Some times:
First time I tried, It came after the first F5-attack
Second time I needed 5 F5s
And just now it was enough with three
Edit:
The F5-trick don't seem to work anymore
It was working for me at the time GoldBit mentioned it but now it is down for me too.