My Opera—like many other high-traffic sites—uses caching. That caching can sometimes—like during this week’s DDoS attack be a bit too potent. One of the factors behind the caching is the User-Agent (UA) header your browser sends. As Opera’s many variations are the most frequently seen UAs on the My Opera site, it is also the most likely to be hit by this.
Disclosure: I’m an employee of Opera Software. Opinions are my own, yadayada.