Annoying Treo problem

My Treo has decided that it no longer wants to alert me to phone calls. Well, not exactly. It'll ring for a call and then reset the phone to not ring and not vibrate. So all it does it light up. Yeah, not so very helpful. A soft reset didn't help this behavior.

Suggestions? Hard reset? Cuss a lot?

I can list what software I have installed though I haven't installed anything new in months and the problem started sometime this week (and btw, if you've called and gotten voice mail, this is why).

Thanks!