Ok, I've been fiddling around with the .pro, trying to organize the source into folders that make sense, rather than just the big blob of files that Carbide makes when it creates a new project.
I've been flipping back and forth between the text and the .pro in-place editor (I know the structure of .pro files.)
Now, all of a sudden, the .pro in-place editor no longer comes up - complains there is no OLE registration (presumably in the registry) for that type of file.
If I shut down Carbide and re-open, same issue. If I create a new (Qt) project, same issue.
What's the deal? I must have broken something... Is the development environment so insanely fragile that stuff just stops working if you look at it wrong?