Congratulations! I think it's definitely worth a shot to try to get the updated CV in. In my field I think it would definitely be possible as long as the adcomm hasn't started reviewing my file yet. If you have been in contact with admissions people at the universities then perhaps you could ask them if you could submit it as an addendum?
Take it from me as a someone on the second go around, there is life if you don't get in on your first attempt - I look at my second go around as getting a second opportunity, this time with a lot more experience. All is not lost for this year though, there is still a long way to go this year and you may still get admitted to your first choice school. All the best!
I agree with Bison. You really do not know if there will be other rounds of invites after the interviews so there is still hope yet. Perhaps you can check the survey results from last year to see if admits to your dream program were given out later in the season. Also, why the feeling of doom? Ultimately it is not the school that you go to that is going to determine your level of future success, sure it might be better at a top school, but it is still very possible to work your way to the top of your field even if you don't go to an elite university.
I think it would be weird, I don't think I've ever seen GRE scores on a resume before (I don't even think most grad applicants would put their GRE on their resume, so I'd imagine it'd be even weirder for a non-academic position). If you have your degree already you could put that on there with any honors you've received. If you haven't finished school yet I think you could put some relevant courses you've done along with their grades.
Remember the GRE is not very important for most places, and I'm guessing that for Ivy League schools they'd be even less important, once you meet some minimum cut off, which I'd imagine that your scores would.
That's good that your LoR writer finally sent them in. If the application system didn't allow the LoR writer to upload it because she was late, perhaps the department has an email address that the letter could be sent to - just ask them about that.
I doubt it that this automatically means you're rejected. Check out the survey results on this page for UIUC CS - they gave out some admits in February last year, and since they were remarkably consistent this year with the first wave of acceptances (sent Jan 12 last year and Jan 11 this year), I'm guessing that they will have admits to give out in February of this year as well.
Don't quit! Be a pest! Keep emailing, texting, calling visiting (if you have to). It's a pain, I know - I've been there, but it's your future we're talking about here. The LoR writers mean well, but writing letters can be low on their list of priorities, so you just have to keep reminding them until they get it done. Just keep pressuring them (politely of course) until it gets done.
I'll be turning 30 (gasp) in the Fall so I don't think its too late. A prof I met with last August pointed out that I was older than most applicants, but he said that could be an advantage since most people who start in their early 20s don't have a firm idea of what they want to study and change their minds often, he said.