how to change "project owner" using PSI 2010

Hi everyone,

I've just faced a weird situation. when I'm going to change "project owner" via PSI, it returns error 1056 (Invalid project owner) except when the user is in "administrator" group. I'm sure it doesn't matter which groups the user belongs to ,either administrator or project manager or even team member to be a project owner.

var projectDataSet =this.GetProjectDataSet(projectInfo.ProjectUID);var orginalProject =this.GetProject(projectInfo.ProjectUID, projectDataSet);var sessionUID =this.CheckOutProject(projectInfo.ProjectUID);if(!string.IsNullOrEmpty(projectInfo.ProjectOwnerName)){var resourceManager =newResource();var ownerResource = resourceManager.GetResource(projectInfo.ProjectOwnerName);if(ownerResource ==null){thrownewException("this is not valid");}
            orginalProject.ProjectOwnerID= ownerResource.ResourceUID;}this.UpdateProject(sessionUID, projectDataSet);

I would appreciate any help

Best regards