[EVO 4G General] k2buckley:
I promise that you can be bricked at the bootloader. I promise. I used to think the same as you, that if you can get to the bootloader, you'd be able to recover. Well, after trying to help a few people out in the past couple weeks, (and even having one of the devices in my hands), I determined that you CAN INDEED be bricked at the bootloader. How? I have no idea. Why? I have no idea. You tell me if you know any other ways to get out of the bootloader when this is what happens. I'd love to know.

Here's the situation: You're at the bootloader, S off. When you try to boot the phone nomally, it loops at the splash screen (not boot animation, just the htc evo screen). Over and over. Pull battery. Boot back to bootloader. Select recovery. Loops at the splash screen, same thing.

Okay, try flashing a new recovery, right? no problem....right? Flash PC36IMG of Amon Ra 2.3. Everything seems to be successful, no errors. Boot to recovery. Splash screen loops. (wtf?) Okay, try a different recovery, or a different copy of recovery, right? Flash the new PC36IMG. No errors. Boot to recovery. Splash screen loops.

Hmm, interesting, but still no problem, right? Try using fastboot to erase current recovery, then flash a new one. That should work, right? Same thing, all seems to be a success, no errors, until you try to boot, or boot to recovery. Same thing. Splash screen loops. Try again, just to be sure. Same thing, splash loops

Okaaaay,...hmm? Last resort, run RUU. Ran RUU. RUU completes successfully. Sweet, that must've worked. Reboot the phone normally. Splash screen loop. Battery pull, bootloader. Recovery. Guess what? Splash screen loops. Well, hmm you think to yourself. What now? A different RUU right? Try it again. Runs with no errors. Reboot. Splash screen loops. WTF??? Okay, lets try the RUU as a PC36IMG. It runs, no errors. Same result (splash screen loops). Hmm, lets try another RUU. Runs again. Same result. Hmm, lets try using fastboot to command the RUU flash. That must work, right...RIGHT?? Fastboot flash the RUU, no errors. Reboot. You guessed it, splash screen loops.

So now what? Maybe the SD card is corrupt, lets try booting without the sd card in (getting desperate now, try anything). Same results, splash loops. Lets try formatting the SD card, then flash a PC36IMG ruu. Same results.

Now, keep in mind that these cases were all S off. There was no way to turn S on, due to not being able to flash Unrevoked S on tool in recovery (because there was no way to get recovery), and RUU would not turn the S back on (except in two cases, but that was because they had never used unrevoked forever, and were on the Eng .76 bootloader)

I have no idea what caused these situations. All of them reported that it happened out of nowhere. Do I think it was a specific ROM that caused the issues? At this point, I don't. The problem has happened on a few different ROMs. Do I think it was user error, not really. At least not in all the cases. I believe that there was some freak coincidence of hardware failures, for whatever reason, who knows. Things go wrong.

And in case you didn't get a chance to read the 28 page thread about it, here ya go. http://xdaforums.com/showthread.php?t=1009672

If it was as simple as running an RUU, or flashing a new recovery, do you think the thread would've went 28 pages, and still not have found a solution? (and quite a few 'regulars' who know what they are doing dropped in that thread and tried to help out, and still no solution was found)

So I tell ya, you can end up being bricked at the bootloader.

EDIT: and by the way, ADB won't recognize the device when it's in this state. You can use ADB in recovery, or any time after the boot animation starts, and when it's in the Android OS, obviously. Since we have no recovery, and can't get past the splash screen, there is no ADB. Just fastboot, which you can only do so much with in this situation.