Compile a project and then, without closing Inform 7, look in the “Build” directory of the project. There should be a file in there called “Debug log.txt”: open it in a text editor and have a look for any lines starting
Bad ref was
If there are any, paste them and then following few lines: this should be printed in the debug log as the result of that internal error.
Wow. Indeed there is. And it’s quite a lot.
And here they go:
EDIT - I’m sorry, there’s just too many lines, it makes the thread hard to browse. I’ll PM it to you.
Hmmm, unfortunately, I have to conceed that I don’t know what that means: it seems to be a problem coming from somewhere deep in the compiler.
The only thing I can suggest is that this might come from the compiler trying to index extension documentation - try removing the extensions you’ve got in “My Documents” and see if that helps.
This is worth filing as a bug in Mantis (mention the “Bad ref was” line, but you don’t need what comes after it, as that doesn’t seem too interesting). Hopefully Graham might shed some light on it. (Though he’s currently on holiday.)
Thank you very much, you’ve helped me locate the problem.
I have every extension in My Documents. Even built-ins. I know it’s considered bad form to move the built-ins to the My Documents folder, but with new versions coming out, and me never knowing which version Inform will pick, I prefer to have it all in one place.
And it seemed there was a clash between the standard rules I had and the standard rules in the newly installed directory. See, I thought only the three reported extensions in the change log had been changed, and so I didn’t move any other extension. Never crossed my mind that I also had to move Standard Rules.
So I guess that’s that. Thank you very much for helping me fix my problem, you were a lifesaver. 
Phew, glad we found it. In general you can expect the standard rules to change every version.
As an aside, you can direct Inform to use a particular location for extensions etc. by creating a “home.txt” file (see the help under “Windows Inform Notes” on the help menu) that can be useful if you want multiple versions installed.
Actually, I tried that as soon as the feature came out. It didn’t work very well, for some reason, so I just neverminded it. Anyway, thanks for the help again. 