Sucks for you... all this stuff about letters of rec, grades, etc... is just a sham; the reality is that the schools admit everybody who takes the Oct 18 exam and reject everybody else
Actually, I'm pretty sure you're OK. I found this tidbit on the Harvard application which makes it sound like you just need to get them your scores as fast as possible, even if they're not ready by the time you submit the application:
Official score reports must be submitted by the Educational Testing Service. If the GRE Subject test is required or recommended by the program, it is advisable to have the scores submitted to us as soon as they are available. If you have recently taken the GREs or will be taking them soon, provide date above.
Also, if you want, you can always call on Dec 10th, pay the $12, and write in your scores on the application. I'm sure they'll provisionally 'take your word' on the scores until the official reports arrive