HTC Desire 500 stuck in bootloop. What can I do?

[AC Question]

HTC DESIRE 500 bootloop!

hi,

I have a desire 500 with simlock to Austrian Provider A1.
I did never root or flash my phone in the past.

The problem: I start my phone and it freezes at the green HTC Logo. I can't start it any more.

Bootloader Menu shows:
***LOCKED***
Z3U PVT SHIP S-ON RL
HBOOT-1.0.01.0001
RADIO-14.08.36Q4.301
OS-1.15.161.2
eMMC-boot
Sep 3 2013, 16:50:38.0

HBOOT
<VOL UP> to previous item
<VOL DOWN> to next item
<POWER> to select item

FASTBOOT
RECOVERY
FACTORY RESET
SIMLOCK
SHOW BARCODE

I tried a factory reset, but without success.
The sim card was destroyed since it loops. ( i could not put the sim in another phone to work).

my tries:

fastboot with htcdev unlock:
i can unlock till the screen shows wheter to unlock or reboot. If I try unlock with the volume + - keys it vibrates 7 times, and nothing other happens.
I can move with the volume buttons again.

fastboot params:

fastboot getvar all

version: 0.5
version-bootloader: 1.01.0001
version-baseband: 14.08.36Q4.301
version-cpld: None
version-microp: None
version-main: 1.15.161.2
version-misc: PVT SHIP S-ON
serialno:
imei:
meid:
product: z4u
platform: HBOOT-8x25Q
modelid: 0P3Z11200
cidnum: VODAP120
batter-status: good
batter-voltage:4180mV
partition-layout: HTC
security: on
build-mode: SHIP
boot-mode: FASTBOOT
commitno-bootloader: dirty-818106b78e
hbootpreupdate: 12
gencheckpt: 0
all: Done!
finished. total time: 0.031s

has anyone any idea how to get my phone working again ?
Please help.

thx,

Klaus