Joshua Szulecki , May 04, 2008; 06:05 p.m.
To help everybody giving advice, could you post a sample of the image you are having a problem with, along with the relevant settings and filter information?
My guess is that you probably needed a stronger, or possibly differently edged, filter, but I'd like to see a sample. Using a sky with a lot of white as practice might not be fair to yourself. ;)