Sharepoint: Issue Adding SPUser to SPGroup FBA & Windows Auth

[Arielle]

Foreword: Our Sharepoint site runs off both Forms Based and Windows Authentication. That being said some users have dual accounts for both methods of authentication. ..but not all users. Each account has unique ID's but runs off different SSPs.

Problem: Currently working on a tool that one piece (the one I need help with) is having issues adding users to a specified SharePoint group. I am getting a legitimate SPUser but when I try to add that SPUser to the SPGroup it throws an error whenever that SPUser is an AD SPUser as opposed to one from the Forms-Based Authentication.

    protected void AddUserToGroup(string strUserName)
    {
      SPWeb oWeb = SPContext.Current.Web;
      SPUser oUser = getSPUser(strUserName);
      if (oUser != null)
      {
        oWeb.AllowUnsafeUpdates = true;
        SPGroup oCurrentGroup = oWeb.Groups[gstrListGroup];
        lblStatus.Text += oUser.Name + ": ";
        try
        {
          oCurrentGroup.AddUser(oUser);
          lblStatus.Text += "Complete<br>";
        }
        catch (Exception)
        {
          lblStatus.Text += "Error occured. Please check the name or add the user via the Sharepoint Group<br>";
        }
        finally
        {
          oCurrentGroup.Update();
        }
        oWeb.AllowUnsafeUpdates = false;
      }
    }
 

I have also tried to hard-code manually add the AD account and I still get the error. It tells me that the user is not unique or does not exist which does not make any sense to me because when I go to SharePoint directly I see the SPUser, I see their properties and their unique ID.

Could this possibly be a case where if the user may no longer exist in AD but still has a SharePoint account that they may be throwing this error?

[Ashwini Rudra]

Even I am geting same issue. Any solution?

[RW5207]

Did you ever figure this out? I'm using PowerShell and getting a similar result: Set-SPUser : The user does not exist or is not unique.