Rendering to a cubemap: resolution limitation?

Greetings!

We are trying to render a scene to a cubemap, but beyond the 512 resolution, we get the following error message:

screenviewcoord[1] < 0 || screenviewcoord[3] < 0

UnityEngine.Camera:RenderToCubemap(Cubemap)

The offending code is:

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent (typeof (Camera))]
 public class RenderCube: MonoBehaviour {
     Cubemap DynamicCube = null;
     
     void Start () {
     DynamicCube = new Cubemap(1024, TextureFormat.ARGB32, false);
     }
 
     void Update () {
 
         Debug.Log("Rendering to dynamic cubemap");
         gameObject.camera.RenderToCubemap(DynamicCube);     
     }
 }

Is there a built-in limitation on the resolution of a cubemap render?

Anyone could help us here?

Thanks!