[Tauro78]

ya lo arregle:

Código Delphi [-]
 
privatevoid treeView1_NodeMouseClick(object sender, TreeNodeMouseClickEventArgs e)
{
if (treeView1.Nodes[0].Nodes[2].Nodes[0].IsSelected)
  {    
    frmCuentasAltas frmCA = frmCuentasAltas.InstanciaSingleton();
    frmCA.MdiParent = this.MdiParent;
    frmCA.Show(Owner); 
  }
}