It would seem odd that both either hoses or calipers wopuld go at the same time though. I'd be looking more toward something that they share, be it the e-brake, rear hard line feed, or even master cylinder. I have only had something similar happen once- I had a front caliper seize on me, it caused a horrible vibration and when I stopped and got out to check (at night) I could see the disc was glowing bright red. This was on my 82 300CD with 3 year old calipers on it