I just got this reply from PNY tech support:
It is set to 5ns but can safely be overclocked to 4ns BUT please be
aware that we do not support or instruct overclocking the video cards as
this can void the warranty.
Thank you,
PNY Tech Support, USA
Still seems like a good card though, even if it only has 4ns ram. Gainward may be a better bet though at 4.5ns. I'm undecided myself, might wait and find out what the Gainward cards are like, and if that refresh rate problem mentioned is a design fault or a one-off.