I had the same Problem with cracked Modells if they are not only one mesh. So you only could solve the Problem by making the whole modell to one mesh.
@Hybrid: What do you say is the best supported modell format into Irrlicht? I want to know this because our modellartist wants to know into witch format he should save the modell data.
For static models probably .x format as it supports smoothed normals. The 3ds loader does not and I'm not sure for .obj. Only if you are using lightmaps you will need something else.
For animations it's either .x or .b3d (or .ms3d if you own Milkshape). Only if you have simple keyframed animations it might be good to use .md2. .md3 is available as a patch, might also be worth looking at - it should become part of Irrlicht sooner or later (I just wanted to see if the .b3d integration already cleans up the animation interface - .md3 will bring some more methods for the AMSN interface).