Having Adobe CS4 and Mac OS X Snow Leopard both installed is very likely to mess up Quick Look of Flash ActionScript (.as) and Flex (.mxml) files. Most inconvenient for those used to browsing through the files and looking into them by just hitting the Space key.

Fortunately, there's qlcoloecode – A Quick Look plugin for source code with syntax highlighting. With just a bit of tweaking you can have your AS/MXML Quick Look back:

  1. Download qlcoloecode
  2. Copy the downloaded QLColorCode.qlgenerator file to /Library/QuickLook
  3. Right-click QLColorCode.qlgenerator
  4. Choose Show Package
  5. Locate the Info.plist file
  6. Find the LSItemContentTypes key and add the following string to the array:

You should now be able to Quick Look your AS/MXML files.

Despite the fact that AS3 syntax highlighting of qlcoloecode is a bit shoddy, it's still far better than just the AS file icon:

Quick Look AS3 syntax highlighting