If you have ever used QuickTime Pro 7.x to do an “Export for web”, then embedded the resulting movie in a web page, it would be a good idea to check to make sure those movies are still playing.
Apparently Apple made a change with their servers in early April that has broken some movies embedded using this method, potentially effecting thousands of web sites. The symptom is the movie will not stream after clicking on the poster frame.
Unfortunately this must be replaced on each page containing an embedded movie. This issue does not effect movies exported to web from Snow Leopard’s QuickTime X.