when you create an HG repository and push files to that repository that contain a .git folder or a .gitignore file the repository will be unreachable and the server sends an 404 "Resource not found". You then can't do anything with the repo not even deleting it in the webfrontend.
Deleting the .git* stuff from the filesystem on the server resolves the problem. All files where pushed ok to the repository.
Tested on OS X with MacHG as a client and on OS X for the server.