I too received errors (three times) trying to purchase an upgrade. I went in and looked at my reservation and found I no longer had a seat assignment. I reselected a seat in first class and it let me but I've been checking my credit card account and have not been charged for the upgrade after a week. I'm trying to decide whether I should call or not. The actual flights isn't until mid-December so I have time. I know that ethically I should call and probably will tomorrow.