Problems with velocity in Unity 5

Hi. When I do GetComponent().velocity = new Vector3(speed, 0f,0f); in Start function to a Unity Cube, the cube moves well. However when I do the same in a own object (model with 3d Studio) the object stop.

I have created a physic material without friction and the gameObject rigidbody properties (Unity cube or my own gameObject) have Drag 0, Angular Drag 0, gravity enabled and isKinematic disabled;

Thanks and sorry for my English level

try reducing the mass of your object.

try somehing like:

GetComponet<Rigidbody>().velocity = speedvector;

The project was created in Unity 4.6. Today I updated to unity 5. In v4.6 the object works well, but in v5 the object stop.

In the other hand, I fix the problem apply GetComponent().velocity = new Vector3(1,0,0) in the FixedUpdate function.