Re: Registering components under XULRunner 24

I have copied the XPCOMUtils.jsm from a recent firefox install. Still doesn't work. I have then registered a console listener. The error message I see is:

Could not read chrome manifest 'file:///G:/mozilla24/xulrunner'.

as already mentioned above, I am creating the file like this

nsCOMPtr<nsILocalFile> file(do_CreateInstance("@mozilla.org/file/local;1", &retval));
nsILocalFile *greDir;
retval = directory->Get(NS_GRE_DIR, NS_GET_IID(nsILocalFile), (void **)&greDir);
file->InitWithFile(greDir);
file->AppendRelativePath(NS_LITERAL_STRING("components/components.manifest"));

//later: registrar->AutoRegister(file); 

It seems the file I pass to the AutoRegister method is not valid. In particular, the part I add via AppendRelativePath seems to get lost, but why?? I've tried all permutations I can come up with, still the same...