The reason foxnews doesn't work is because they use wmode transparency on their flash scripts. This is more of a browser issue than flash, and should be fixed when ff3.0 comes out.
Also I found a way to see the live CNN videos. You need three things.
1. Install User Agent switcher
2. Add to it a mac user agent string.
3. Assuming you use mplayerplug-in, download the source
and edit mplayerplug-in/Source/plugin-setup.cpp
In the file look for "NPError GetValue(NPPVariable variable, void *value)"
Below it find the string that has "Windows Media Player" and add Flip4Mac to the end of the string.
Then ./configure, make, and su make install.
4. To test go to CNN site using the mac string and live video should work.