Google Product Forums
Re: Wifi Hotspot Not working error message "Mobile Data network unavailable or invalid sim"
GianniM Jan 24, 2012 6:19 PM
Posted in group: Google Mobile Help Forum

Categories: Android Devices : Android Applications :

Thanks a lot for the tip. I had the same problem
with a T-Mobile Samsung Exhibit II 4G that I had unlocked and rooted.

I used Titanium to uninstall TetheringManager, and after that
tethering worked!

(I am on Mobilicity in Canada)