Irrlicht Engine

It's a very strange problem.
When i load my scene graph exported by irrEdit,named "a.irr",it always gave the error"Could not load mesh, because file could not be opened: : boundingbox.obj"
I'm sure there are no path problems,what's the reason?
BTW,if only custom scene nodes by irrEdit like cube,sphere are in the irr files,it would not give errors.

Are you sure?

Have you checked that in irrEdit the working directory is your application direcory?(maybe that path is incorrect, not the one in your code).