https://en.bitcoin.it/wiki/Mining_Hardware_Comparison

5770 sits at around 150 Mhash/s there

try checking what version of the ati sdk you have.

http://bitcointalk.org/index.php?topic=4308.msg62882#msg62882

seems most get the best result with 2.2

Hope it helps mate

Okay, seems to be the same im using.

are you using the extra flags "-v -w128"?

What miner are you using?
On my 5750 i got about 115 Mhash/s with poclbm.