So, SE18 is sitting there doing nothing, but nevertheless it is using 12% of a quad core PC to not do it. This time, the CPU usage doesn't stop as soon as SE gets focus, so I was able to run the profiler for a minute or so (result attached).
Speaking of which, when I saved the profiler data I browsed to the right folder, chose a filename, clicked OK and instead of saving I got another save dialog! In this one the path and filename in the filename edit box were as I'd set, but the folder view was to my project. I clicked OK and it saved.
However, I then chose to load the profile data, pointed to the saved file and SE says no file exists. Huh? I think the profiling infrastructure needs another round of debugging or something.