Checked again and suddenly not showing any seat reservation at all. Called and explained. Agent would only guess at the cause of me not being able to change it, as well as the reason for it dropping altogether. Now I'm reserved where I want to be, but I'm unwilling to pay an extra $100 for my wife's seat. I'll cross my fingers that SEN seat blocking keeps it open for her. If it doesn't, hopefully that means the flight will be full and an upgrade would be in our stars.