Hi Everyone,
After abandoning this issue for almost a year, I finally resolved this issue, and thought I’d share the solution for anyone else who has this problem in the future.
The short answer is that I didn’t go far enough. After I built the component in debug mode, I correctly GAC’ed the DLL and updated the reference for the calling project to point to the Debug version and updated the Admin Console Reference to the Debug version, then restarted the Host Instance.
At this point, when I did “Attach to Process” within the custom component, the breakpoints were still appearing with the same message as before: “The Breakpoint will not currently be hit. No Symbols have been loaded for this document.”
However, when I “ignored” this error and proceeded with submitting a message through BizTalk, the custom component “woke up” and realized that it was going to be called. The breakpoint errors went away, and debugging worked exactly as it was supposed to!
YAY!
Thanks to those of you who pointed me in the right direction.