I searched my .wine & .netflix-desktop directories for any instances of xpcom. I couldn't find it. So I tried sudo apt-get remove netflix-desktop. It went through the motions but I still have the .netflix-desktop folder with a bunch of stuff inside. It didn't go through a Mono uninstall or Gecko uninstall.
I tried reinstalling but that didn't get me anywhere.
So I went to my Windows computer and looked for xpcom. I found xpcom.dll in C:\Program Files (x86)\Mozilla Firefox. I also found xpcom.js in ...\AppData\Roaming\Mozilla\Firefox\Profiles\r4rsk718.default\extensions\OneClickDownload@OneClickDownload.com\resources\api-utils\lib
I copied them to a flash drive, went to the .netflix-desktop folder and put xpcom.dll in the "Mozilla Firefox" app folder. There is no AppData folder in the user folder in .netflix-desktop but "Application Data" is there with nothing in it.
So if you could tell me where you find xpcom.??? in your installation, I could try pasting the xpcom files in there.