Well, a few hours before T-24 (before FRA-IAD), I tried to checkin thinking maybe it goes by first segment. I couldnt remember since its been a while since I had to deal with not being able to choose E+. That's when I got the error. I guess it did checkin me. Enough so that I could not choose seats from the reservations screen. At that point I decided to goto TK's site to at least get some seats there. Maybe that was a mistake.

I'll try twitter. I thought about calling in after TK has departed but wondered if UA customer service would question how I'm able to do that if I'm suppose to be on a plane. Also, I figure worst case, they can goto the UA counter at IST and get seats then possibly)