I have the same problem as you:I got it unlocked,finally..using the htc dev method. i'm now running the viperS5 rom,i recently installed it...running smooth so far but I didn't go through the whole method to install it as needed. just run the zip in recovery and it worked. thought I was gonna brick the phone seeing that I didn't go through the full method because i'm a kind of noob,so I bypassed some stuff.
Code:
[email protected]:~/workspace/Android/AndroidSDK/platform-tools$ sudo fastboot flash unlocktoken Unlock_code.bin
sending 'unlocktoken' (0 KB)...
OKAY [ 0.152s]
writing 'unlocktoken'...
FAILED (remote: unlock token check failed)
finished. total time: 0.159s