Sometimes, when you have too many programs running on your computer, or too many processes, like tons of other anti viruses, web browsers, stuff like that, your computer doesn't have enough power to handle so much work! So, the "Java SE Platform Binary", or, the Spiral Knights program, doesn't get enough processing power, and freezes. Just try closing it with Alt+F4, then reopening Spiral Knights. Hope this helps!
~~~Godmodeman of the Black Magic Clan~~~