I don't have the Hero3, but my riding partner Matthew had a few seconds of pink at the beginning of some Hero1 footage from one of our rides. At first I was like "oh sh_t!" because it just happened to be a clip we wanted to keep (steep singlespeed climb), but the pink went away after a few seconds. It was also during the descent, so no worries.

I had an entire mtb ride recorded with no sound once on my Hero 960 (good thing I was also recording with my helmet-mounted ContourHD!). I formatted the card after that, and from my Google searches I found that other people had that problem when they pressed the record button too soon after turning on the camera. Now I wait a few seconds after the power-on beep before pressing record. No more problems so far.

BTW, the audio on your Hero3 sounds excellent! MUCH better than the Hero2, so you can make some good-sounding videos now

Also, I bought a second Hero2 about a month or two ago for $199 at REI. As of a couple weeks ago they still had them in stock.