December 18, 2003 - 10:51
The QuickTime 6 MPEG-2 Playback Component for Mac OS X (D2187) stopped working on 15 December. This was a bug and Apple have posted a fix which you can download from the Apple Store, if you purchased from there originally.
Apparently you will also be able to download the new component if you have a valid FCP4 or DVDSP2 serial number. The problem is discussed here.