"Access is forbidden" during create organization network

Hello,

  I encounter a problem while I'm trying to create an organization network using Java SDK :

    com.vmware.vcloud.sdk.VCloudException: Access is forbidden
              at com.vmware.vcloud.sdk.Response.handleUnExpectedResponse(Response.java:132)
              at com.vmware.vcloud.sdk.SdkUtil.validateResponse(SdkUtil.java:189)
              at com.vmware.vcloud.sdk.SdkUtil.get(SdkUtil.java:99)
              at com.vmware.vcloud.sdk.VcloudResource.getResourceByReference(VcloudResource.java:107)
              at com.vmware.vcloud.sdk.Task.getTaskByReference(Task.java:113)

  Sometimes it passes without a glitch, but other times I see the above exception on my console

  Why this is happening ? And how to avoid this issue ?

Thank you