HP OfficeJet 4500 Wireless (G510n) crashes on PC Fax

Hi @all,
I have a strange problem with my HP OficeJet 4500 Wireless (Model G510n):

I run Ubuntu 11.10 and the printer is connected via wireless lan.

hp-check -t brings up:
-----------------------------------------

HP Linux Imaging and Printing System (ver. 3.12.10a)
Dependency/Version Check Utility ver. 15

Copyright (c) 2001-14 Hewlett-Packard Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.

Note: hp-check can be run in three modes:
1. Compile-time check mode (-c or --compile): Use this mode before compiling the HPLIP supplied tarball (.tar.gz or .run) to determine if the proper
dependencies are installed to successfully compile HPLIP.
2. Run-time check mode (-r or --run): Use this mode to determine if a distro supplied package (.deb, .rpm, etc) or an already built HPLIP supplied
tarball has the proper dependencies installed to successfully run.
3. Both compile- and run-time check mode (-b or --both) (Default): This mode will check both of the above cases (both compile- and run-time
dependencies).

Check types:
a. EXTERNALDEP - External Dependencies
b. GENERALDEP - General Dependencies (required both at compile and run time)
c. COMPILEDEP - Compile time Dependencies
d. [All are run-time checks]
PYEXT SCANCONF QUEUES PERMISSION

Status Types:
    OK
    MISSING - Missing Dependency or Permission or Plug-in
    INCOMPAT - Incompatible dependency-version or Plugin-version

Saving output in log file: /home/rolandcg/hp-check.log

Initializing. Please wait...

---------------
| SYSTEM INFO |
---------------

 Kernel: 3.0.0-26-generic-pae #43-Ubuntu SMP Tue Sep 25 17:39:44 UTC 2012 GNU/Linux
 Host: asus
 Proc: 3.0.0-26-generic-pae #43-Ubuntu SMP Tue Sep 25 17:39:44 UTC 2012 GNU/Linux
 Distribution: ubuntu 11.10

-----------------------
| HPLIP CONFIGURATION |
-----------------------

HPLIP-Version: HPLIP 3.12.10a
HPLIP-Home: /usr/share/hplip
HPLIP-Installation: Auto installation is supported for ubuntu distro 11.10 version

Current contents of '/etc/hp/hplip.conf' file:
# hplip.conf. Generated from hplip.conf.in by configure.

[hplip]
version=3.12.10a

[dirs]
home=/usr/share/hplip
run=/var/run
ppd=/usr/share/ppd/HP
ppdbase=/usr/share/ppd
doc=/usr/share/doc/hplip-3.12.10a
icon=/usr/share/applications
cupsbackend=/usr/lib/cups/backend
cupsfilter=/usr/lib/cups/filter
drv=/usr/share/cups/drv/hp

# Following values are determined at configure time and cannot be changed.
[configure]
network-build=yes
libusb01-build=no
pp-build=no
gui-build=yes
scanner-build=yes
fax-build=yes
dbus-build=yes
cups11-build=no
doc-build=yes
shadow-build=no
hpijs-install=no
foomatic-drv-install=no
foomatic-ppd-install=no
foomatic-rip-hplip-install=no
hpcups-install=yes
cups-drv-install=yes
cups-ppd-install=no
internal-tag=3.12.10a
restricted-build=no
ui-toolkit=qt4
qt3=no
qt4=yes
policy-kit=no
hpijs-only-build=no
lite-build=no
udev-acl-rules=yes
udev_sysfs_rules=no
hpcups-only-build=no
hpijs-only-build=no

Current contents of '/var/lib/hp/hplip.state' file:
[plugin]
installed = 1
eula = 1
version = 3.12.10a

Current contents of '~/.hplip/hplip.conf' file:
[upgrade]
notify_upgrade=true
last_upgraded_time=1350581403
pending_upgrade_time=0
latest_available_version=3.12.10a

[settings]
systray_visible=0
systray_messages=0

[last_used]
device_uri="hpfax:/net/Officejet_4500_G510n-z?ip=192.168.178.37"
printer_name=Officejet_4500_G510n-z_fax
working_dir=.

[commands]
scan=/usr/bin/xsane -V %SANE_URI%

[refresh]
rate=30
enable=true
type=1

[polling]
enable=false
interval=5
device_list=

[fax]
voice_phone=
email_address=

 <Package-name> <Package-Desc> <Required/Optional> <Min-Version> <Installed-Version> <Status> <Comment>

--------------------------
| External Dependencies |
--------------------------

 gs Ghostscript REQUIRED 7.05 9.04 OK -
 network Network-wget OPTIONAL - 1.12 OK -
 dbus DBus REQUIRED - 1.4.14 OK -
 scanimage Shell-Scanning OPTIONAL 1.0 1.0.22 OK -
 policykit Admin-Policy-framework OPTIONAL - 0.102 OK -
 xsane SANE-GUI OPTIONAL 0.9 0.998 OK -
 cups CUPS REQUIRED 1.1 1.5.0 OK 'CUPS Scheduler is running'

-------------------------
| General Dependencies |
-------------------------

 reportlab Python-PDF-Lib OPTIONAL 2.0 2.5 OK -
 libcrypto OpenSSL-Crypto-Lib REQUIRED - 1.0.0 OK -
 pil Python-Image-Lib OPTIONAL - 1.1.7 OK -
 pyqt4-dbus PyQt4-DBUS REQUIRED 4.0 4.8.5 OK -
 libjpeg JPEG-Lib REQUIRED - - OK -
 libpthread POSIX-Threads-Lib REQUIRED - 2.13 OK -
 python-dbus Python-DBUS REQUIRED 0.80.0 0.84.0 OK -
 python-devel Python-SDK REQUIRED 2.2 2.7.2 OK -
 pyqt4 Python-Qt4 REQUIRED 4.0 4.8.5 OK -
 cups-devel CUPS-SDK REQUIRED - 1.5.0 OK -
 sane-devel SANE-SDK REQUIRED - 1.0.22 OK -
 libusb USB-Lib REQUIRED - 1.0 OK -
 sane Scan-Lib REQUIRED - 1.0.22 OK -
 cups-image CUPS-Image-Lib REQUIRED - 1.5.0 OK -
 libnetsnmp-devel SNMP-Networking-SDK REQUIRED 5.0.9 5.4.3 OK -
 python-xml Python-XML-Lib REQUIRED - 2.0.1 OK -
 python-notify Desktop-notifications OPTIONAL - - OK -

------------------------------
| Compile Time Dependencies |
------------------------------

 gcc gcc-Compiler REQUIRED - 4.6.1 OK -
 libtool Build-tools REQUIRED - 2.4 OK -
 make GNU-Build-tools REQUIRED 3.0 3.81 OK -

----------------------
| Python Extentions |
----------------------

 cupsext CUPS-Extension REQUIRED - 3.12.10a OK -
 pcardext PhotoCard-Extension REQUIRED - 3.12.10a OK -
 hpmudext IO-Extension REQUIRED - 3.12.10a OK -

-----------------------
| Scan Configuration |
-----------------------

 hpaio HPLIP-SANE-Backend REQUIRED - 3.12.10a OK 'hpaio found in /etc/sane.d/dll.conf'
 scanext Scan-SANE-Extension REQUIRED - 3.12.10a OK -

------------------------------
| DISCOVERED SCANNER DEVICES |
------------------------------

device `hpaio:/net/Officejet_4500_G510n-z?ip=192.168.178.37' is a Hewlett-Packard Officejet_4500_G510n-z all-in-one

--------------------------
| DISCOVERED USB DEVICES |
--------------------------

No devices found.

---------------------------------
| INSTALLED CUPS PRINTER QUEUES |
---------------------------------

Brother_DCP-115C
----------------
Type: Unknown
Device URI: usb://Brother/DCP-115C?serial=BROH6F951503
PPD: /etc/cups/ppd/Brother_DCP-115C.ppd
PPD Description: Brother MFC-210C CUPS v1.1
Printer status: printer Brother_DCP-115C disabled since Wed 10 Oct 2012 08:24:46 PM CEST -
 Unplugged or turned off

Officejet_4500_G510n-z
----------------------
Type: Printer
Device URI: hp:/net/Officejet_4500_G510n-z?ip=192.168.178.37
PPD: /etc/cups/ppd/Officejet_4500_G510n-z.ppd
PPD Description: HP Officejet 4500 g510n-z, hpcups 3.12.10a
Printer status: printer Officejet_4500_G510n-z is idle. enabled since Thu 18 Oct 2012 08:14:54 PM CEST
Communication status: Good

Officejet_4500_G510n-z_fax
--------------------------
Type: Fax
Device URI: hpfax:/net/Officejet_4500_G510n-z?ip=192.168.178.37
PPD: /etc/cups/ppd/Officejet_4500_G510n-z_fax.ppd
PPD Description: HP Fax hpcups
Printer status: printer Officejet_4500_G510n-z_fax is idle. enabled since Sat 20 Oct 2012 01:56:36 PM CEST
 Rendering completed
Communication status: Good

--------------
| PERMISSION |
--------------

groups user-groups Required - - OK root lp lpadmin

-----------
| SUMMARY |
-----------

Missing Required Dependencies
-----------------------------
None

Missing Optional Dependencies
-----------------------------
None

Total Errors: 0
Total Warnings: 1

Done.
-------------------------
Everything works fine, scanning, printing, making copies in BW and color and even sending a fax from the device works fine.
My problem ist: i cannot send a fax from my PC.
There is no error message on my pc, but the device is blinking and rebooting while building up the connection (the opposite fax is ringing, though). When the OfficeJet is rebooted, it prints out a power loss failure statement.

What can I do?
I tried deleting hplip with synaptic and installing a fresh version from console.
I searched with google
I rebooted... nothing..

Please help!

Thanks