First of all, thank you very much for your answer.

To download de videos using HiDownload, the only thing that i had to do, is to modify the options of RSTP streaming, declaring to use HTTP , throw port 80.

I try to do everything you said me, but i can not manage to play the videos.. when i installed the K-Lite Mega Codec Pack (version 1.55 i think) package that you said me and used the Media Player Classic, the player says that the file cannot be opened.

I also try with VLC, but nothing happens, just a initial screen, and then its freezed...

Related to the format of the videos, I?m sure (not 100%) that this link
rtsp://vstream.acm.org/10.1145/OOPSLA2005/1094855_768K/p11-ungar.mp4
is to a Quicktime Video, because if I use the QuickTime Player to open the URL, it works perfect.

Well, if anyone can try to download the videos and telling me what happen I will be glad! Because, is just some bad installation or an incorrect version in my system.

Thanks again!
ClaudioA