Trying to resolve my tethering issue after leaked OTA upgrade to JB ( Tethering after JB update? ), I deleted some system files. My bad... doing so did no harm in ICS. Should not have taken the chance in JB.
After reboot I'm stuck at the swirling red droid logo. Tried to get into factory reset, but can't get past android exclamation mark (no response to volume up & down, eventually reboots).
Here's what I did, per: Help - Using a DROID 4 in Canada..
3) Open Root Explorer and go into /system/app folder, press the "mount r/w" button and rename the following files to .2 :
4) Copy the build.prop using Root explorer to build.prop.2 and edit the build.prop in a text editor with the following changes:
ro.telephony.gsm-routes-us-smsc = 0
ro.cdma.home.operator.isnan = 0
ro.mot.lte_on_cdma = 0
ro.cdma.subscription = 0
Save the file an exit, always keep build.prop.2 around just in case you ever need to roll back
I have backups of the files I messed, obviously, but can't get back in to fix this mess.