Anyone else having these issues?
My system generally works the same now as it did before the upgrade as far as AVI files are concerned—i.e., some "supported" files play in the QT X Player and all "supported" files play in the QT 7 Player.
All my old .avi movies will work but no new ones.
Since AVI is a file type, the real question here is whether or not both old and new files contain the same compression formats and if different, whether or not the non-playing compression formats are supported by by your codec component configuration and in the AVI file type. To test the possibility that certain codecs are no longer compatible with QT X v10.2 in the AVI container, try playing the problem files in the QT 7 v7.6.6 player app.