Assertion Error on b2Body

gistfile1.cpp

m_World = new b2World(m_Gravity,m_DoSleep);

b2BodyDef bd;

//some code here: starts a for loop

bd.type			= (b2BodyType) f->GetKeyValue<int>("type");

bd.gravityScale		= f->GetKeyValue<float>("gravity");

bd.angle		= f->GetKeyValue<float>("angle");

bd.angularDamping	= f->GetKeyValue<float>("angular_damping");

bd.angularVelocity	= f->GetKeyValue<float>("angular_velocity");

bd.linearDamping	= f->GetKeyValue<float>("linear_damping");

bd.linearVelocity.x 	= f->GetKeyValue<float>("linear_velocity_x");

bd.linearVelocity.y 	= f->GetKeyValue<float>("linear_velocity_y");

bd.awake		= f->GetKeyValue<bool>("awake");

bd.position.x		= f->GetKeyValue<float>("position_x");

bd.position.y		= f->GetKeyValue<float>("position_y");

t->m_Body = m_World->CreateBody( &bd );

//some other code here: ends the for loop