Default [Q] Freezes after applying downgrade via AAHK2

Hello,

I wanted to root my HTC Desire HD with AAHK2. At first it worked fine, connected to my phone, said that it needs to downgrade, went into hboot and did the necessary tasks.
Now I am unable to boot my smartphone. It freezes at the HTC logo. The same in HBOOT - it also freezes.
HBOOT shows me following info:
ACE PVT SHIP S-ON RL
HBOOT-0.85.0024
MICROP-0438
RADIO-26.09.04.11_M2
eMMC-boot
Apr 12 2011,00:55:45


I removed micro SD and sim and were successful in doing a fastboot. After that I did a factory reset but that did not change things either.

Somebody knows what I should do now (except buying a new phone )

Greetings in advance!