This happens both with the Win64 build (on Win7) and the Linux x64 build (on Ubuntu 12.04.1 LTS x64). I haven't tried other builds.
If I'm in the "Editor Windows" options dialog, some disabled items don't appear to be disabled:
- New file tab position
- Hidden file extensions
But you can't do anything with them (unless you change the related option that enables them). In 18.0.1.2, these items are dimmed so it's clear that they are disabled.
Also, the following item is disabled (and not dimmed) and doesn't seem to have a way to enable it:
- Hide known file extensions
So there seems to be no way to turn that option on.
