Does this link work for you...

So i have been using drop box and unity together for ages…when i visit this link locally its works fine, but when i visit it using the dropbox public link it says ive not installed webplayer (I have)
Can someone test it please:

https://dl.dropbox.com/u/4633015/unity_tests/TREX/WebPlayer/WebPlayer.html

Works fine… Nice Dino!

check your firewall settings, etc

must be something like that I’d guess