Math.Sign(int.MaxValue);
I hit F11 to step into it and it steps right over it. I have all the options set for debugging .NET framework source (I think).
Edit: for someone with Visual Studio 2008 SP1 and .NET 3.5 SP1 who can step into this line successfully: what is the size of your .pdb file?
Edit 2: because I can successfully step into System.Windows.Forms, I'm fairly certain I have a corrupted symbol cache, but every time I try to reload the symbols, it re-downloads as only 763KiB.
Edit 3: Is it possible that it I can't step into System.Math.Sign because System.Math source code simply isn't released/available?