Cannot Access Dell Preferred Account

I recently received a Dell gift card which I have been trying to use.  At some point when I try to buy the item I've selected, the prompt asks me to verify my Dell Preferred Account by entering my mother's maiden name and my Social Security Number.  I am not making a mistake in entering the information but the web site refuses to verify my account, so there must be something wrong with the information Dell has on me.  How do I go about correcting this problem?  Thanks for any help!