Maybe, some people have noted that we are facing spam attacks since last night
http://www.physicsoverflow.org/13810/blocking-spam-ip-addresses
The spamming from unregistered IPs is getting worse, so I have (temporarily) set the permissions to post questions, answers, and comments to "Registered users", until we find a better solution for these issues.
If this does not help either, might even have to set the permissions to post anything to "Registered users with email address confirmed" ...