I've found that all WMV files are damaged and unusable when downloading with LW4.8.1 and Mac OS X 10.2.8.

The problem you're having with the .avi files is that they were compressed with the Intel Video CODEC, which is not available on OS X. They may play fine in Mac OS 9.x, but then again, they may not.

Any info on the corruption/issues with WMV files?