Am I the only one that got a CSR that tried to be a dick about this, then? He had me run through all the tests, which RR'd my Xbox twice, but because on the final test it just hung at the Xbox logo instead of RR'ing he told me they wouldn't fix it for free. I had to keep insisting that even if it wasn't red-ringing right now, it had done it several times that day and during that same phone call. After talking with his supervisor or something for about ten minutes he finally came back on the line and completed my repair order.
The freezing and maybe even the lines was something mine did in the day or two leading up to its death. I was thinking "damn, is Fallout 3 glitchy." Does it beep when it freezes? Mine did that. Anyway, maybe you can leave it on a day or so running some software that will tax it and heat it up and see what happens. It might just be ready to go.