The new one is missing the magnet that the phone uses to detect if the cover is on or not. The mmc is forcibly unmounted whent he cover is removed. Your new el cheapo cover has no magnet, therefore the phone believes the cover is missing ergo the mmc is never mounted.
I really thought after all this time the device has been out that everyone knew about the magnet attatched to the rear stand and what happens if it is not there. The mind boggles lol