I'm really at my wit's end with this one!

My SMS/MMS keeps shutting down. When I use the native app, I get this "process.com.mms (or whatever) has stopped" and then I have to force shutdown.

I started using Handcent, thinking it would fix the problem. It didn't. This time, the handcent app shuts down.

This is getting really annoying. I wish I knew what caused this so I could maybe fix the problem. But it happens so randomly at times, I don't know.