It would appear I've been caught in this as well.

Scheduled to fly UA838 TPE-NRT and UA852 NRT-SFO on March 28. It's showing UA838 as a 777 and UA852 with a blank next to equipment. It still has my seat assignments, but won't load the seat map. I'm gonna be pretty bummed if I lose my upgrade having to switch to another flight.

edit: would it behoove me to try and call United to get on the other flight and hopefully transfer the upgrade before United starts informing people about this?