It’s probably an issue with the encoding codec. perhaps try uninstalling it and reinstalling it. I just recently had a similar thing happen. I was using Sorenson to encode some media to FLV using the ON2 VP6 codec and I was getting pink frames at the beginning of my media. I tried re-encoding on a different computer and they worked fine. Must’ve been something with the codec on that particular computer…
Also, if you’re using something like Nucleo for rendering out of AE, sometimes that gave me errored files too…