Problem with Handcent- Keeps showing old messages as new.

[Clak]

I've had this problem for a while now. Handcent keeps popping up with notifications of new text messages, but it's an old message it's notifying me about. It's been going on for a while and I'm getting really tired of it. Even afraid it may be interfering with the sending of new messages as I've been told that some folks aren't getting my texts.