Check if your card is properly seated into its slot. Using some canned air for the slot and some rubber rubbing on the card's golden pins wouldn't harm.
Check the power cord from the PSU to the GPU is properly seated. If possible, use another connector. Further, if possible, try another PSU.
Uninstall and reinstall FlashPlayer.
Run a GPU memory test, like
Cuda GPU memtest, since anomalies often are a symptom of a failing memory chip.