+1  A: 

An important change in JS XPCOM components in Fx4 is that they now need to be registered in the chrome.manifest, see this page of documentation on the changes.

Erik Vold
I know that. I have this registered in the chrome.manifest file the problem is when I try to create the NSGetFactory.
Jesus Ramos
var NSGetFactory = XPCOMUtils.generateNSGetFactory([jsshellclient]); tries to create this factory and it complains about the CID being incorrect.
Jesus Ramos
and you made the required changes to the chrome.manifest? and you're sure that those changes are correctly done? if not then can you please post your chrome.manifest?
Erik Vold
I fixed that issue now (stupid mistake on my part, forgot to apply function) but my extension will not run, it just initializes the js files and does nothing. Do I need to specify an app-startup or something so the extension .start() gets called?
Jesus Ramos