Pamsel in distress again?
My best guess, without chem #s, is that the 'sand' is calcium - I'd say that when the #s come in, you'll see high-ish pH, alk and calcium - it's the classic combo for calcium precipitation. Lowering the pH will help absorb it back into suspension in the water, you may have to drop the alk as well - the calcium is only going to go away via draining the pool . edit (some of the watere, not the whole thing!) - end edit

I hope that this was what you wanted in your pm - last night I didn't even log on, the weekly 'safety meeting' at my boss' house went into extra innings

Please take care, it's good to 'see' you again! If you've more ?s, you know what to do. After you get this cleared up I HOPE that you have nothing but a wonderful summer enjoying your pool!!