With cudaminer I am getting a reject rate as high as 25%, anyway I could fix this? For an ati card what would be a good miner to use for clevermining? What kind of rate could I expect to get for a ati card that costs around $350?
Don't mine Scrypt with a GPU. You're wasting your money.
You'll be certain to pay more for electricity than you'll earn.
If you want to mine Scrypt, get an ASIC.
If you want to mine with GPUs, mine something else like X11, X13 or one of the many others that have varying profitability over time.