Its not really a bug. Its just that Apple has implemented a very poor color converter in Quicktime Pro. Basically, Apple’s response is “What do you expect for a $30 piece of software?” The fact that QT Pro has the exact same feature set on the PC as the mac is supposed to be good enough (the mac version has many of the same problems with color).
About the only thing you can do on the PC, because QT7 still hasn’t been well integrated into any of the popular encoding apps, is to use a different H.264 encoder. The encoder in Squeeze 4.3 is OK, and should handle color pretty well and offer compatibility with QT7 play back. The Nero (ATeme) encoder is better, and its output should be compatible with QT7 play back as well. For overall quality, I currently really like the encoder from MainConcept, but its output is not directly compatible with QT7. There is also the open-source x.264 project, but again, QT7 compatibility is not easily achieved.