i never used Blender myself, so i'm not sure what is wrong there.
OgreMax viewer should open it and is a good checking tool, what errors does it find? (btw, if I remember correctly, it opens binary form not xml form)
OgreMax is one of the best exporters and even it can be got confused sometimes, when object is translated rotated etc. So if you did such manupulations to your object(s) that may be the cause. i.e. do not translate/rotate your objects but translate/rotate its vertices.