Never use the UA website for international fares. You will be put on other airlines, quoted absurdly high fares, and sent on the most improbable routings. Just dial the toll free number. You will save time. You will save money. You will get more miles (remember that there aren't the bonus miles on TG or BD).

I've had some success on domestic itineraries on the UA website. And I'll check the UA website out of curiosity. But it really takes some time-consuming tinkering in the multi city mode.

Just call.