Perhaps you have parented the camera to the mesh ?
Attempting to scale the camera with ScaleMesh would just cause a fatal error, as the camera doesn't have any mesh data. Scaling the camera with ScaleEntity would cause the near and far clipping planes to scale but the size of the mesh would be unaffected.
Like blackbag said, make sure you're using a float variable to store the scale value you wish to apply (assuming you're using a variable in your code).