I see you've not got a response yet, so I'll go out on a limb.
At a guess, some of the file type associations that you need may not be assigned to Quicktime.
To check, launch the Player. Under Edit, go to Quicktime Preferences. Click the Browser tab. Nera the bottom of the window, there's a Mime Settings button.
If that's not it, I'm not sure what your problem might be. QT 7.62 works OK for me under Win7 X64. I'm using an "unofficial" build at the moment, but it worked under the beta (7000) and the RC (7100) as well.
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