Doctrine problem

<?php defined('SYSPATH') or die('No direct script access.');

/** @MappedSuperclass
  * @HasLifecycleCallbacks
  */
class Model_File extends Model_Base
{
    public function hasGroup ($group) {
        foreach ($this->groups as $g) {
            if ($g->id == $group->id) return true;
        }
        return false;
    }

    public function clearGroups () {
        $em = Doctrine::instance();
        $this->groups = new \Doctrine\Common\Collections\ArrayCollection();
        $em->persist($this);

        try
        {
            $em->flush();
            return true;
        } catch (Exception $e) {
            echo $e->getMessage();
            return false;
        }
    }

    public function addGroup (Model_Group $group) {
        if (get_class($group) == 'Model_Group') {
            if (!$this->hasGroup($group)) {
                $em = Doctrine::instance();

                $this->groups->add($group);

                if (get_class($this) == 'Model_File_Item') {
                    $group->files->add($this);
                } else if (get_class($this) == 'Model_File_Dir') {
                    $group->dirs->add($this);
                }

                $em->persist($group);
                $em->persist($this);
                $em->flush();
            }
        }
    }

    public function setGroups($groups) {
        $this->clearGroups();
        $admin = Model_Group::getAdminGroup();
        $em = Doctrine::instance();

        $adminIsInGroups = false;
        foreach ($groups as $group) {

            if ($group = Model_Group::load($group)) {
                $this->groups->add($group);
                if (get_called_class() == 'Model_File_Item') {
                    $group->files->add($this);
                } else if (get_called_class() == 'Model_File_Dir') {
                    $group->dirs->add($this);
                }
                $em->persist($this);
                $em->persist($group);
            }
        }

        $this->addGroup($admin);

        try
        {
            $em->flush();
            return true;
        } catch (Exception $e) {
            echo $e->getMessage();
        }
        return false;
    }

    public function setGroupsRecursive ($groups) {
        $this->clearGroups();

        $childs = $this->contents();
        if (count($childs) > 0) {
            foreach ($childs as $child) {
                if (get_class($child) == 'Model_File_Item') {
                    $child->setGroups($groups);
                } else if (get_class($child) == 'Model_File_Dir') {
                    $child->setGroupsRecursive($groups);
                }
            }
        }

        $admin = Model_Group::getAdminGroup();

        $em = Doctrine::instance();

        $adminIsInGroups = false;
        foreach ($groups as $group) {
            if ($group == $admin->id) $adminIsInGroups = true;

            if ($group = Model_Group::load($group)) {
                $this->groups->add($group);
                $group->dirs->add($this);

                $em->persist($this);
                $em->persist($group);
            }
        }

        $this->addGroup($admin);

        try
        {
            $em->flush();
            return true;
        } catch (Exception $e) {
            echo $e->getMessage();
        }
        return false;
    }
}