Can't play VDO tutorials of Apple's web sites

Question

I'm using Mac mini with Mac OS X 10.7.1 in school's proxy server. The port of proxy is 8080.
My problem is my mac can not play VDO tutorials of Apple's web sites,http://www.apple.com/iwork/tutorials/#pages-hero (and other VDO of Apple).
Every attempt to play these VDO, there is a authorization pop-up asking for username and password of the proxy server. There is no VDO after filling it but soon another authorization pop-up again.
I called Apple technical support. He asked me go through Youtube and movie download from iTunes. All of those were OK. He concluded that the only problem is VDO streaming and send my case to his superior (senior advisor). Apple's senior advisor said that "probably" there is a problem with the setting of the server. The technical support team admitted that they are not familiar with networking.
I asked our IT, he suspected that my problems came from Mac software. He said that Windows PC use the same proxy port to view those VDO tutorials but Mac software change the port of VDO streaming from 8080 to 80 (they checked it). This is the first problem. So every attempt to play that VDO requires new authorization with user name and password. The second problem, Mac software would not accept the username and password that required by proxy server for the new port.  So, no matter how often I filled up username and password it won't work.
Help, please.

Answer 1

I was having problems opening some downloads (using VUZE) using quicktime
Are you referring to "Vuze" the "torrent" app? If so, then what was the source and compression formats for the files you downloaded? While I would expect Apple files directly downloaded from the Apple site to be compatible with the QT player, files posted by other sources could be in any compression format and would either trigger the message you got, not play, or not even load to the player. The normal work flow in such situations is to determine what compression formats were used to encode the downloaded file and then install the same components if available for your system--not arbitrarily download QT components which have not useful function or which may create component conflicts.
Neither of which could I also get to open my downloads, so I deleted the file.
What file did you delete--the downloaded installer, the installed component, the QT Player, the video file you downloaded, or something else?
Now I can not play any of the videos on the Apple website.
How are you trying to view them? In a browser? Opening the file as a URL in the QT Player? As a downloaded file?
Quicktime is the diverted program but I have no idea what to do from here. Can anyone please please help me with this.
Have no idea what you are talking about here. Is this a setting in the Vuze software? If so, you need to go the Vuze forum to get more information.
I should add, I have sound when I play the tutorials. just no visual, and I get no message to download QT either.
Once again, how are you viewing the video? What compression formats are involved? If using the QT Player, what does the "Inspector" window or Finder "Info" window say about the file?