I read in 2ch that SE is controlling access from certain ISPs and IP address, trying to track down the attacker/hacker.
Some JPs with certain ISPs cannot log in, but some with another type can. Some can log in play, but some cannot access AH.... Then the next day, the same people that didn't have problems will have problems...etc. etc.
On a related note, I spoke with my family back home in Japan, and they told me that Japan has been receiving cyber attacks from China regarding the recent text-book issue (I'm sure you've seen in on Lou Dobbs). There was a large demonstration in China against Japan, and several Japanese businesses, restaurants and consulates were attacked by Chinese mobs (as in ppl folks...not monsters).
I don't know if SE's servers are being attacked as a part of this or if it is some other entity (perhaps an angered RMTer?) but nevertheless, I'm going to be harvesting rock salts now.