Also: still looking for people to be an officer as mentioned in my post before.
All of you guys in this thread have been invited to the guild...
@Waller: I had the same problem: Close all other programs, launch Spiral knights go to options/just press "esc" while playing, change the display mode lower (mine's the lowest one, it helps... A LOT), never go full-screen, change graphics settings to low (Graphics are still amazing). Go to Video options, uncheck
everything and then check the box next to "Compatibility mode"
That should take care of the worst

(Cleaning up your desktop, moving folders somewhere else, and only having shortcuts on your desktop can also help. Watch that your desktop background isn't a picture with WAY too many pixels that you won't even get to see...)
That's about all that helps, hope it'll work for you