I found out by accident that if you begin drawing the symbol for a spell, if you immediately tap the inventory button, everything in the game will stop, except for you.It doesn't cause any technical problems with the game afterwards, and to restart time again, you just need to start another spell without interruption. You can't activate anything like doors or switches, or even shadow realm portals, but it can be very useful. I'm not sure if it works on every Ds, but it works for both of mine. Hope this helps, Kidfox.
The crystals you collect during gameplay that enhance certain abilities will fade, crack and crumble and are removed from your stock along with their powers. If you highlight the crystal before it breaks and select 'Drop' and then pick it up the crystal will be replenished.