In case you use the nice little library ASZip to create zip files from Flex, be aware that there’s a bug in the released code v0.2, but that there’s a patch. The bug is described and a patch provided in Issue 1. The same bug causes Excel to not like the files, Issue 2.
Just thought I’d blog about this since I rediscovered and refixed the bug before realizing the issue tracker had a patch. I’m not sure why the patch isn’t checked in; apparently the author forgot about it or was otherwise prevented from working on the library more.