My daughter's 8330 has the same problem off and on since she convinced me to update her software in October (she doesn't have a computer, so she had to get me to do it). It worked fine for months before the software update.
The first time this happened it spontaneously "fixed itself" after a few days. At least that's what she said. Don't know if she did something to it like restarting it or a battery pull or what. It acted up again last week and it seems to have fixed itself again because she's answering it again. Since it's the only phone she has, it drives me crazy more than her when it doesn't work, because I can't reach her at all.
I don't know if the software update is corrupt or it's because she treats her phone like garbage, tossing it onto tables or into her purse from several feet away (sometimes missing the purse altogether), etc. She bought this one used after accidentally tossing her Pearl out the window of her minivan (she was pulling her purse out of the back and it fell out of the purse and out of the window, and was never seen again 
).
I haven't had a chance to look at her profiles settings. She insists that there's nothing amiss, but she's not as technically adept as I am, so I'm not sure that she's been as thorough as need be. I also don't know how to advise her because the only BB I've ever had is my Bold 9000 and the settings may be entirely different on hers.
Mostly, she's just hoping to hold out until she's eligible for an upgrade next month, but if she keeps treating her phones this way, the next one won't last long either, especially if it gets thrown out the window like her Pearl did.
In the meantime, I wish I knew what the solution was to this or that someone would post one. At this rate, it will probably happen to my daughter's phone again before she gets a new one.
Not sure what you all mean by a "hard reset." Are you referring to a battery pull?
