Are you using a DS Lite? It's probably just a tight fit since it's based on the dust cover. Either that or the casing isn't screwed together right.
Do you mean into the slot on the DS or removing the circuit from one case and into the other? If it's the second I can post pictures if it helps.
thanks mr hanky and other guy, i found out that i wasnt supposed to line up the circuit board with the screw hole.