[HTC One V] worldindo1:
NOTE: This one's a big one if you can't tell! Everyone give a round of applause to simonsimons34 for tracking down the issue. What does this mean? Well, there may not be a need to ever downgrade using the RUU. If you go here (you really can't miss that big, bolded "here"), you will see that he determined the issue is caused by:

He also took the liberty of building a kernel compatible with 4.2 and putting in a commit for fixing the kernel to work with the newer radio at GitHub. Any ROM builders who see this, please do check it out. As far as everything goes, I haven't personally tested it but I do always encourage people to try it out. Simon has been a great supporter and kernel builder for our device so I have faith that he hath found the Holy Grail. 'Course my thread will have no more existential purpose, BUT it is a great resource so as it is, I will leave it up for the general perusal of the community. Have a great week everybody and I look forward to a new flood of development.

Exciting news y'all! This thread has been stickied! [Hopefully] this will allow continued support and growth of the thread. My personal philosophy is that anything I post shouldn't be locked down to what I know or believe in, so I encourage any reader to put forth their input. What does that mean? It means that if you have a suggestion, by all means inbox me your thoughts. I'm open to continual development of this tutorial through community teamwork. Have a good day everyone!

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Here are some common reasons why your phone will randomly reboot (bootloop). You should only use an RUU (the methods below the "=" signs) if NOTHING ELSE WORKS (because the RUU does a factory wipe of the phone).

Common Problems:

I switched from another ROM and now my phone keeps rebooting...

There are several factors in play here. The commonly accepted fix is backing up your data and doing a full wipe (cache, dalvik cache, system, data) followed by reflashing your ROM.

I upgraded my ROM from blah blah version to blah blah version (ex. 4.0.x to 4.1.x)...

This is because your old Ice Cream Sandwich system stuff may not be compatible with JellyBean (in the case of the example). Wipe system and the caches (dalvik & cache) followed by reflashing your ROM.

I upgraded my ROM (within the same version) and it keeps rebooting...

Every time I upgrade my ROM, I wipe cache. If something funky happens, just wipe system and reflash your ROM.

I flashed a ROM and it won't boot at all...

Either you flashed a ROM for a different device, you flashed a kernel for another device, OR you didn't flash a kernel at all. Make sure everything is for your phone (the HTC One V on Virgin Mobile is the CDMA version known as "PrimoC" whereas the GSM version is the "PrimoU").

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NOTE: This guide is for the One V!

I know the feeling! You're all excited because you just unlocked your One V's bootloader, flashed a recovery, and flashed a steamin' hot new ROM. You boot up for the first time and get ecstatic, the tension building as you put in your Gmail info. You finish the start up but OH NO!!! Your phone reboots! You blame yourself... you blame your cat... you blame your wife... you blame the war in the Middle East. You think, I must've done something wrong! Stupid, stupid, stupid! Don't fret! Take my experience with this quite seriously (despite the jokes). For 2 weeks, I retraced my steps and tried EVERYTHING! I thought it was just the ROM's problem, so I flashed one after another to the same end. Finally, I decided to post a new thread asking for help. Nothing became of the first thread, so I posted a second one. To my great relief, along trotted Curiousn00b. After shoving me in the correct direction, I figured out the rest. A big thanks by the way, Curiousn00b! The following is the method that I used to get my phone to finally run a ROM. Also, a thanks to CafeKampuchia for the quoted directions below.

A few things to make sure you have:

Windows (with Administrator's priveleges)

Fastboot installed and working

Your phone (duh!)

A USB cable

Time and patience

The following quote is from CafeKampuchia's thread over here.

NOTE ABOUT THE FOLLOWING PARAGRAPH: jmztaylor's site is now legally able to host the RUUs again so the download link is right here*

In support of jmztaylor and all of his work for this device, I have decided to also include his website in this thread... *here is the download directory for the HTC One (Primo) device RUUs. I'm not sure if this bug effects other Primo devices, so this especially pertains to the PrimoC (HTC One V CDMA). Thanks jmz for the tip!

Solution #1

Thus far you should have the stock recovery back and be bootlocked again. Now, back in fastboot mode, you should already be connected to your computer via USB (if you disconnected, just reconnect it and wait for "FASTBOOT" to change to "FASTBOOT USB")

Run this command:

fastboot oem rebootRUU

Next, start up the RUU program again and let it run through without interruption. After this process is done, the phone should boot up to the stock ROM. Let it do its thing, but this time don't do the OTA update. From here, just unlock the bootloader again, install your recovery of choice, and install your ROM of choice or reroot the stock ROM (I know some want to keep it stock).

As also pointed out by RoyalYeo, you can let HBOOT take care of the problem:

Solution #2

My personal solution (Solution #1) is the more technical side of things and also exposes you to the nitty-gritty. Having said this, #1 is quite touchy because if you do something wrong, there is a good chance that you could... well uh, brick your phone to be quite honest. On the other hand, #1 requires no SD card (given the event that your SD card won't mount, your SD reader is broken, or you just plain don't have an SD card). Ultimately, the choice is up to you.