Thanks exTermia for this submission.
Microsoft have issued a fix for Windows Media Player 9 & 10 that fixes color smearing or a bleeding effect when you play MPEG4 videos.
According to the knowledge base article at Microsoft, this is caused by the MPEG4 codec, sometimes using invalid motion vectors.
In Microsoft Windows Media Player 9 or 10, you may experience a color smearing or bleeding effect when you play some MPEG4 videos. This behavior often occurs when the video contains fast-moving scenes of varying colors.
This problem occurs because of an issue with the way that the MPEG4 codec handles motion vectors. Sometimes, the decoder mistakenly uses invalid motion vectors.