Been seeing similar for the last couple of days - any posted vid either never plays, plays for a few seconds then dies, or when an attempt is made to download it, Safari gets started, then almost immediately stops, reporting "The network connection was lost", usually after actually downloading a total of ('scuse me while I go get the exact number... There it is) The last three I tried to download all managed to transfer the same 174K before being stopped. (They all show various expected sizes, ranging from 3 megs to 10.5 megs)
All of them showing 174K getting transferred before aborting strongly suggests to me that the initial handshake is happening like it should, then the server is timing out for some reason that, without further information, can only be guessed at.