Then, I found that another programmer in our group had forgotten to add a new file to source control and had, thus, broken the build. I patched around that. He will neither be the first, nor last programmer to forget to put a file into source control. (Been there, done that.)
Then, I went to test the failed integration with another of our sister applications and discovered what our QE team has not yet found, because I am on a newer version of the source than they are currently using. The programmer above decided to fix our COM initialization, but -- sadly -- did not actually succeed in doing so everywhere, with the result that the integration with the second sister application now does not work at all.
I think we are all very tired on this bus.