Thread:Extension talk:CategoryTree/Version page is empty after install

When I finished installing the extension (not working for me, yet), I've noticed that the Special:Version page, where I supposed to see the version of the extension, is now empty and there is no extension. If I delete the require_once line of the extension, it's all back to normal.

I didn't see anything wrong with permissions or in the log. Does anybody know what could cause this or where I was wrong?

Thanks!