My account has been frozen today for making reservations of any kind. I can access the reservations page fine as long as I am not logged in. But as soon as I log in, the reservations page is replaced with: "We’re sorry, but united.com was unable to complete your request."

I called 1K who connected me to web support. The issue was duplicated on three different machines with three different browsers. All the usual cookie/cache/etc clearing had no effect. The kicker: "There are only two people who can fix your account, they won't be in until Monday." What a 24/7 airline! Time for the three trips and $6000 I was about to spend to go elsewhere. [My plans are too complex and initially notional to call 1K reservations. I can do that after a couple hours of research, which I won't be doing...]