For those of you on HBOOT 1.50, you can now downgrade your HTC Evo 3D back to HBOOT 1.40. This requires that you have a Windows/Mac and a Ubuntu(linux) computer (or you can do it all in Ubuntu). You can also use Ubuntu running on VirtualBox.
For Mac, change all adb to ./adb-mac and fastboot to ./fastboot-mac. For Linux, change all adb to ./adb-linux and fastboot to ./fastboot-linux.
Also you will need