I got this error from setup:
(I downloaded a new one but i got the same error)
http://wiki.spiralknights.com/File:Sem_t%C3%ADtulo.jpg
AND desktop Icon:
http://wiki.spiralknights.com/File:Sem_t%C3%ADtulo2.jpg
Yesterday i was playing fine but today i can't open my game through icons.
I have spiral knights on my desktop and everytime i click on it it goes to a number like 4% then stops and doesnt move and i left my device on for 5 hours and it didnt budge... Everything up to date, java and on intel website everything downloaded, so any game master can help me out here please :)
Most likely Java is not pointed to the game directory in the shortcut you're using.
Check the properties of the shortcut you have to make sure that the "start in" directory is the one the game is installed in (where getdown-pro.jar is that it can't find). On Windows Vista/7 that would usually be ":\Users\\AppData\Roaming\Three Rings Design\Spiral Knights".
If you're using an old shortcut or have moved the game directory or the shortcut itself this could explain why it's doing this.