.nxs file question

hi, i'm new about NxOgre, a strange question bothers me those days.
i use NxOgre 1.5.5 and i have a triangle .nxs file (which is 1.5mb), i want to use it as the ground of my racing game.
then i write like this

NxOgre::ResourceSystem::getSingleton()->openArchive("Tracks","file:../../media/models/tracks/common");
std::string nxs = "Tracks:road002.nxs";
NxOgre::Mesh*triangleMesh = NxOgre::MeshManager::getSingleton()->load(nxs.c_str());

NxOgre::TriangleGeometry*triangleGeometry = new NxOgre::TriangleGeometry(triangleMesh);
PhycisSystem::getScene()->createSceneGeometry(triangleGeometry);

then under the debug mode it work fine, but when i turn it to the release mode, it crashed when i delete NxWord.

later, i use a mush smaller .nxs file(cube.1m.nxs), it work fine both under debug and release, just like this.

NxOgre::ResourceSystem::getSingleton()->openArchive("Tracks","file:../../media/models/");
std::string nxs = "Tracks:cube.1m.nxs";
NxOgre::Mesh*triangleMesh = NxOgre::MeshManager::getSingleton()->load(nxs.c_str());

NxOgre::TriangleGeometry*triangleGeometry = new NxOgre::TriangleGeometry(triangleMesh);
PhycisSystem::getScene()->createSceneGeometry(triangleGeometry);


is anyone who knows it ?
my english is pool and i hope u can understand me.
thanks very much...