The forums are currently being focused by some Ukrainian "hackers" for malicious attacks. As a result I have taken the forums offline as I work to sure up the forum security and protect against future attacks.
The activity on the Nexus sites will hopefully go unhindered during this down-time.
There's no reason to believe this is an attack focused on the community, rather just an attack on a popular message board that can provide the hackers with access to some potentially unsecured computers. I would like to reiterate that if you are browsing the internet without an anti-virus or firewall as a bare minimum of protection then you are very, very open to being exploited by these sorts of hackers.
Update at 23:21
I'm still working on tightening security on the forums and have confined the skin choices to the default forum skin for the time being. It's bright, I know. I'll go to sleep soon and will assess the security situation in the morning. If the hackers have injected some malicious code again it will be back to square one.