Now, for the tip of the day (or week, or whatever...)
In debugging this latest problem, I had to download symbols for various OS components. Internally, we have a pretty vast symbol server that can get you .PDBs for everything that you need. Externally, you can get symbols for many components so that you can debug through them. Nothing beats a good call stack!
Both our internal and external systems use a symbol server to locate the right symbols. We didn't have this until ~2 years ago, and I don't know how we lived without it. Getting the right symbols used to be voodoo -- now it is super easy. Here is a page talking about what you have to do: http://www.microsoft.com/ddk/debugging/symbols.asp.
Also note that with VS.Net you can use this stuff too! Here is a link on that: http://support.microsoft.com/default.aspx?scid=kb;EN-US;q319037