I've been having problems viewing webcasts that provide streaming
video through Internet Explorer 6.0.2.  Neither WMP10 or Real Player
play back any video.  The viewing window is usually blank; sometimes
the viewing window for WMP is green.  The issue was first noticed
after upgraded to WMP 10.  Could be coincidence.  Doesnt totally
explain why Real Player is not working.  Uninstalled WMP10, same
result.  Thought that it could be a codec issue.  Installed DIVX
codec.  Tried 1-2 other codecs as well, same result.  Just installed
Real Player updates to version 10.5, same result.  Vewing videos on
stand alone players (when not viewed through browser) work fine. 
Tested streaming video at
http://www.mcb.wa.gov.au/webcasting/test.htm.  Real player stand-alone
works.  Seems to be problem when video is embedded in IE.  Reset IE
security to lowest levels, and advanced settings are at default
levels.  Firewall shouldn't be issue because it worked previously,
with no recent changes having been made to firewall.

Any ideas?  Thanks for your help.

I suspect an IE issue:
1) Go through IE security settings, line by line. 
Go to your security settings windows, Click "Custom Level". 
Enable everything, especially ActiveX, and playing videos & sounds.

2) Download another browser (Firefox, Netscape) and see if that works.
If it does, then we can narrow the problem to IE.

I went through the "Custom level" security settings, enabled
everything that needed enabling or set options to "low" safety or
"low" security.  Also, all of the webcasts I had on file to test
required Internet Explorer.  Same results with my testing.