If your device boots fine but when you press volume up a @@@ sign appears download [Simple Graphics Mod]
by coderus on http://forum.nitdroid.com/index.php?topic=230.0
and follow the instructions. If all goes well then you will be able to boot nitdroid without your phone shutting down.
If this dosent work reflash your phone again with the nessasary images and again install sillyboot and kernel(Warning YOUR PHONE MIGHT GET BRICKED
Hope I helped