[EVO 4G Android Development] joeykrim:
This has been resolved by using the flash lite exploit to gain root access allowing the misc partition to be flashed with a downgraded main version number which allows the old leaked Eng RUU we have to be flashed!

GUI for how to root

http://xdaforums.com/showthread.php?t=720565

Old and Outdated information from the Original Post listed below for historical purposes ONLY

Who is Affected: If you've flashed the official OTA update on top of a non rooted ROM or your new EVO comes loaded with it, right now it appears there is no way to obtain root...yet!

What is Patched by the OTA: Through the radio.img which the OTA flashes, it updates the Main Version in the bootloader preventing Toast's root methods from working. It also flashes back the stock recovery, removing our root access in recovery mode and ability to apply .zip files. And last of all, the OTA patches the exploit hole in /system/bin/hstools used for unrevoked1 root.

Successfully eliminating all released methods of obtaining root access.

Conclusion:

after going through all these methods with a great helpful member of the unrevoked team, joshua_, this was the final answer:

[22:34] <joeykrim> cant see to find a method to RUU the phone back down ... ive tried all the methods ive seen. any methods i missed?

[22:34] <joshua_> ok, looks like we are hosed then

[22:34] <joshua_> we have a few more tricks up our sleeve sooner or later

Future:

If you have any suggestions/ideas, please post. I might have missed a method.

We will work towards obtaining root for those with new EVOs that have the official OTA applied and those who applied the official OTA.

Details of the tested known root methods:

user debug PC36IMG.zip (toast part 1) - bootloader error - Main Version is older! Update Fail! Do you want to reboot device?

eng build PC36IMG.zip (toast part 2) - bootloader error - Main Version is older! Update Fail! Do you want to reboot device?

RUU_Supersonic_1.32.651.6 extracted rom.zip renamed to PC36IMG.zip - bootloader error - main version is older

RUU_Supersonic_1.32.651.6_Radio_1.39.00.05.31_release_171253_signed.exe - Error [140]: Bootloader version error The ROM Update Utility cannot update your Android. Please get the correct ROM Update Utility and try again.

RUU_Supersonic_1.32.651.1_Radio_1.39.00.04.26_release_171253.exe - Error [140]: Bootloader version error The ROM Update Utility cannot update your Android. Please get the correct ROM Update Utility and try again.

Stock Recovery - Apply update.zip - clockwork recovery update.zip - E:failed to verify whole-file signature E:signature verification failed

flash_image (flash boot or mtd-eng.img) - copied to /sdcard, but sdcard is mounted with noexec. partition with write access for non-root user and allows executing is /data/local . flash_image can't write to the partitions w/o being run with root permissions. chownto and chown of flash_image to user root - permission denied.

##786# - Reset - doesn't seem to effect much in the way of bootloader version ...

Modifying PC36IMG.zip - using a hex editor to attempt at changing the MainVer stored in the android-info.txt, if any bit changes, it seems to fail the validation by the bootloader.