why would Importing an entity fail?

I have the following situation. the uses clicks an add button on a form. I create the entity for the add button in question lets say "Memo"

var memo = Repository.CreateMemo(member);

then I call my dialog box to display the memo

MemoEditForm form = new MemoEditForm(memo);
DialogResult result = form.ShowDialog()

in the constructor for the MemoEditForm. I have the following.

InitializeComponent();
Repository = UnionRepository.CreateRepository();
Repository.ClearAllMemberMemos();
currentMemo = Repository.ImportMemberMemo(memo);
editMode = memo.EntityAspect.EntityState == EntityState.Added ? EditMode.Add : EditMode.Edit;
MemberMemoBS.DataSource = currentMemo;
currentMember = currentMemo.Member;
LoadData();

basically I create a new repository/entity manager. I make sure the entity manager is clear. I import the passed over newly created memo object and import it into the new entity manager. if the user enters all the fields in and then clicks "Save" I close the dialog box and refresh a grid with the new memo. If they click cancel, I remove the entity from the first cache.

This works for the first memo. I add a memo (I click cancel). I click add again and the import this time returns a null for currentMemo.

so my question is why would the import fail. this is my import method

     public MemberMemo ImportMemberMemo(MemberMemo memo)
        {
            if (memo == null || memo.EntityAspect.IsNullOrPendingEntity)
            {
               throw new ArgumentException("Imported memo is null or nullo");
            }
            // Don't bother if already attached to repository's manager
            if (memo.EntityAspect.EntityManager == Manager) return memo;

            ImportEntities(new Object[] { memo });
            return (MemberMemo)Manager.FindEntity(memo.EntityAspect.EntityKey);
        }

    private void ImportEntities(IEnumerable entities)
        {
            EnsureEntitiesAreUnmodified(entities);
            Manager.ImportEntities(entities, MergeStrategy.OverwriteChanges);
        }

yes. It is an identity column.

What i dont understand is that when i pop up the dialog box for Memo form i am creating a new repository before importing the passed in memo object. Why would the previous one still be there?

going back to my example. on the list form, the user clicks Add, i create the memo and pass it to the dialog box form. in the dialog box form, i create a new repository/entity manager, import the passed in memo to the newly created entity manager. if i create a new repository/entity manager, clear it of all memos, and then do the import, should not that one be the only memo in the cache?

Bill