http://www.videolan.org/vlcThe VLC media player can flawlessly handle most, if not all media formats, including streaming formats such as RealPlayer and Quicktime. I do a great amount of video downloading, and have had many files crash my other media players. I have Windows Media Player 10, Media Player Classic, BS Player Pro, WinDVD 7 Pro, RealPlayer, QuickTime, and Power DVD (many don't realize Power DVD is also a media file player). I've had files crash every one of these players, then play without missing a beat on VLC.
The best part is, it's FREE. There are versions for Windoze, Mac OS X, all the major flavors of Linux, Solaris, even BeOS.
Just thought all you fellow multimedia freaks may want to know about this jewel.