I'm sorry if this has been asked before, I tried to find the answer (with no luck). My friend has the TB and I installed the MR2 a few weeks ago (her phone was restarting about 4-5 times a day). Now, I've read if the MR2 is installed on your phone you will NOT receive the update. Is there any way to reset the phone to the previous radio (prior to the MR2), or will I have to due a factory reset. Thanks in advance for your help.
Ok, maybe someone who knows more about this may be able to chime in, but...
First off, I doubt a factory reset would work. A factory reset just wipes all data, but doesn't actually revert your software version to its original factory version...it just leaves you with a refreshed, "blank canvas" of whatever software version you're currently running.
What you can do, if you can deal with a data wipe, is install the full RUU of the new MR2 update. This will pretty much do the same thing a factory reset would do, but leave you with the newest software version.
XDA post where I found the MR2 RUU (with download):
and the original source, with install instructions:
Is there a way for you to upgrade the radio without losing data? To be honest, I don't know. I believe you need to be rooted to flash radio files, so I'm guessing the answer is no, but once again, I don't know the definitive answer to that question.