Christians - could you ever be convinced god does not exist?

[revots33]

This came up in another thread, but I'd be interested to hear from Christians (or believers from other faiths as well).

Is there anything anyone could say, or any event that could happen, that could convince you that your belief in god is erroneous?

I think most athiests agree that they could be convinced god did exist, if proof was presented. (Say, for example, god came to earth and raised my dead grandmother from her grave... I'd certainly believe in god in that case.)

But is there any proof that could make a believer think god DOESN'T exist?

Or, a related question: if you used to believe but no longer do, what changed your mind?