Same problem here. But if I set intensity to 13 the hash rate from cgminer and from the pool are matching at 300 KHashs per card.
Yep. Lower your intensity and you'll see the hash rates matching. I know that's blasphemous, but if the pool is for a young coin then this happens a lot. Also note, and this isn't an accusation, but some pools calculate their payout rate by manually calculating your hash rate. And this manual calculation is, well, lets just say is not always accurate and is under estimated.
![Wink](https://bitcointalk.org/Smileys/default/wink.gif)
Nevertheless, if the coin is young, the DOA/stales might have an effect on your hash rate calculation. Just some ideas...