I've seen it before....
http://www.google.com/search?hl=en&q...r&aq=f&oq=&aqi=
I can reproduce it with Visual Studio 2008 and IE 8 but I think I've also seen it with Express editions and IE7. I think it's also a problem with VS 2010, but I am not sure. Copying it from VS 2010 running in a Virtual PC seems to remove the color so the code gets formatted correctly.
It's easy to reproduce. Just copy some code from VS, paste it in a reply window and hit Preview Post. All code is then messed up. If you use Code tags the code stays OK.
Imar