I second that advice. I had a problem with it choking on the booking and I called reservations and India said that my credit card was bad and that I needed to call Chase. I use it every week and told him that was baloney. So I call Chase and they say the card is just fine. I call reservations back and they cant figure out whats wrong, they dont see the PNR. So I call web support, and they say... yeah, there are problems, hold on... then in a minute its fixed. They manage to "push it through" so that it still processes as a united.com reservation and still gets booking bonus and Chase mileage credit.

So ALWAYS call web support if you have a reservation choke in united.com. They have access to make things happen around the usual reservations processes.