I'm on a Macbook, 2.16Ghz, Intel Core 2 Duo, and 2G SDRAM, with 10.6.7. I've had this problem now for a week and I've tried restarting, resetting Safari, etc. I get the same issue when I use Chrome.
My wife's computer is a Macbook Pro, 2.26Ghz, Intel Core 2 Duo with 2G DDR3, and 10.6.7. She also has the issue.
We don't get any error messages, just no box to see the trailers. I remember it switched some time last week. I regularly visit trailers.apple.com and was surprised to find that some of the movie sites didn't have the button to open the actual trailers. I reset Safari to try and fix the problem, and now all of the trailers lack the button.
This problem has been complained about fairly extensively here:
http://forums.macnn.com/89/macnn-lounge/440032/cant-play-trailers-at-apple-com/
And here:
https://discussions.apple.com/thread/3028251?tstart=0
It doesn't sound like a system-specific problem. Both PCs and Macs are having the issue AND it's happening in different areas of the country (USA - I'm in Miami). Me thinks it's a bug in their coding that they've recently worked on for the site that's hit some machines.
If anyone finds a solution, please post. Apple! Hurry up and fix this!