Have you received any answer from Adobe yet? I've been having the same problem today, but everything was working properly on Sunday. I would really appreciate it if you could let me know once you hear back from Adobe. I'll write an e-mail as well, but I am ouside the US so a phone call would be rather complicated.
Thanks a lot in advance!
I have still not received any response of any sort from Adobe. I suspect they are totally inundated by complaints and queries on their latest suites' failings across differing platforms and do not have sufficient staff to cope. Their Chat "support" kept me hanging about indefinitely to thep oint I gave up waiting. It is a complete disgrace given the charges they are levying for the use of their software.
I used alternative software on a trial basis, called Zoner Photo Studios. IF you get to a point you cannot take any more of this lack of support, you could try them - they were very attentive to technical enquiries...
I did notice however this evening that when I attempted to add photos to Lightroom CC, the error was not repeated, so perhaps have another attempt and see if it has sorted itself out.