[myTouch 4G Android Development] kimbernator:
To senior Mytouch 4gers:

Let's just start recommending the root.sh/visionary method to beginners and people who haven't rooted yet. It might not be the rooting method that causes issues but so far it looks like it plays a role in it. only gfree rooters have had this issue so far, so let's stay on the safe side, huh? just link this thread: http://xdaforums.com/showthread.php?t=834225 and we can notify people later on about whether or not they should use gfree, as it's easy to use even after the root.sh method.

UPDATE:

It turns out that the rooting method may have little to no effect on this issue. Please read the bottom past the "update" title

Most of my data here will be pulled from http://xdaforums.com/showthread.php?t=1074922 and similar threads.

Many of you probably have already read about this, but it has been becoming more and more common for people to get errors in recovery saying that certain partitions cannot be mounted, usually data and/or cache. The issue is that they cannot be re-formatted in recovery because the recovery partition is messed up as well.

Some people escape this using PD15IMG, but about 50% hit another error - Fail-PU in hboot when trying to use this. The only recovery here is available if you have the engineering hboot (Which at this point i would highly recommend you flash). without it, the phone is effectively bricked (I know, i know, not really bricked if you can get to hboot, but it's to the point that there is no recovery and the phone is unusable.)

We have narrowed it down to this: these errors only happen to people who used the gfree method to root. one (convincing) theory was posted in the previously linked thread by xdviper:

In addition to (Hopefully) discovering the issue, we believe we have something you can do to lower your chances of being afflicted by this issue. IF you use the gfree method, reflash recovery a couple times, and hopefully it will work correctly. If you are not in need of a sim unlock, carrier unlock, whatever gfree does, use the visionary method with root.sh. At this point there are no documented cases of these issues happening with users that used that method.

Root.sh method:

http://xdaforums.com/showthread.php?t=834225

Thanks for reading, have fun and be safe!

Mod: I feel it would be beneficial if this thread was stickied.

UPDATE

It turns out that the rooting method may have little to no effect having this issue, in a quote from Guhl99:

I looks like M4G2DE is the bad one and SEMO4G is the good one. We don't have any cases of other ones, but please post yours if it is different. Keep in mind we still aren't 100% sure about this being the cause, but it's very probable, as a logcat on booting in to recovery shows this chip dying. Also be aware that this is a hardware issue, no software can fix this. you have the bad one or you don't.

Also, it would be nice if when you post you would list these things:

1. what method of rooting you used

2. which version of hboot do you have

3. which emmc chip serial do you have

4. have you encountered this issue before

Let's not throw away the idea that the rooting method still plays a big role in this issue! please post any information you have about the partition errors and FAIL-PU errors! All information is welcomed!