Finally! I'm part of the elite! Part of the clique who can now recommend Lutz Roeder's Reflector with full knowledge of its greatness.
Until today, I was just a poser. I knew of Reflector and was keenly aware of what it did. I played with it for a bit but had never in my consulting career come across an instance where I needed to dive that deeply into someone else's code. But I left it installed on my machine because I wanted to pretend to be one of the big boys. And I started to crave the appreciative nods I'd get from better developers when they'd see it prominently displayed on my desktop.
Then lo! An e-mail comes screaming through my Inbox: where is this error message generated for the Franken-app you built that syncs PalmPilot data with Livelink?
(Side note: If I can brag a little, I'm actually kind of proud of that app. Built in .NET, it works better than the application I was trying to mimic on the old software Livelink was replacing.)
The app uses Livelink's API to wedge stuff into the system so after a quick look through Livelink's code base itself to see if the error was there, I dusted off Reflector and pointed it at the API assembly. String search and lo, again! There it is!
So now I can accurately answer that e-mail: It is generated in the receiveOpenResponse method of the LLConnectRouter object in LAPI_NETp.dll.
That should get them off my back, yesno?