It could be that the power draw on the 3.3V line with the acerca and the oc is to high.
Whereas previously there wasn't such a power hungry card on the line.
Or the card is sensitive to small power dips when the cpu starts at 100% causing a momentary drop in voltage until the psu can compensate.

At any rate trying another psu might slove it as that one might have a higher current rating on the 3.3V line and/or a better/faster voltage controller.