Has anyone tried to change an existing reservation online in the last couple days?

Specifically if within the change flight you pick the option"use the value of this ticket to get a new flight" within it, and try to select a new itinerary.

Its giving me a custom error page no matter the browser for that change flight selection.

Using this option, entering your new itinerary, and pressing continue gives error. This is for a simple SEA - LAX being change to something like SEA - JFK or whatever. I would prefer not to cancel and rebook (since this fare has a companion code attatched to it, but I'm seeing the same error on my other itineraries also which are simple cash ones).