I\'ve followed the steps outlined in http://blogs.msdn.com/sburke/archive/2008/01/16/configuring-visual-studio-to-debug-net-framework-source-code.aspx to enable source debug
Debugging didn't work for me when I first followed those steps. I deleted symbol directory and removed all settings from Options -> Debugging -> Symbols and it worked.
Works just fine on Windows 7 x64 with Visual Studio 2008 SP1.