Ok, I don’t know what it is with my OS X install lately after installing OS update 10.5.4 but things seem to be broken left and right. Besides the trash issue in a previous post, Quicktime movies will not play in Safari - but they do play in Firefox. I updated to the latest Quicktime (7.5) and still no go after a restart. After trawling through numerous support forums, this is what worked for me:

  1. Navigate to the "/Library/Internet Plug-Ins" folder
  2. Delete the "QuickTime Plugin.webplugin" file
  3. Restart Safari

Go to http://www.apple.com/trailers to test.