Normal Price Displayed and Charge to Customer Instead of Special Price

Hi, I looked into my Special Price setup after a customer ordered a Special Priced item but was charged the normal price. I searched the forum and this posting but still can't get the issue resolved.

I understand (from Linda's advise) that when manually entering the "Available Date" under the "Product Price Info:" & "Special Price Info:", the format has to be MM/DD/YYYY. Having done that and clicked on the Update button, the entered date automatically changed from 05/01/2006 (MM/DD/YYYY) to 01/05/2006 (DD/MM/YYYY) which is ok so long as it's 1st of May, 2006. Having left the expiry date empty for no expiration, the setup was tested but the normal price is still charge. Cld someone pls. advise me what I have overlooked? TIA.