I see that this problem has already been solved; regardless, I wanted to post what worked for me:
{code}
Dim mStyle as MLeaderStyle = New MLeaderStyle
mStyle.SetTextAttachmentType(TextAttachmentType.AttachmentMiddle, LeaderDirectionType.LeftLeader)
mStyle.SetTextAttachmentType(TextAttachmentType.AttachmentMiddle, LeaderDirectionType.RightLeader)
mStyle.SetTextAttachmentType(TextAttachmentType.AttachmentMiddle, LeaderDirectionType.BottomLeader)
mStyle.SetTextAttachmentType(TextAttachmentType.AttachmentMiddle, LeaderDirectionType.TopLeader)
mStyle.SetTextAttachmentType(TextAttachmentType.AttachmentMiddle, LeaderDirectionType.UnknownLeader)
{code}