Samsung Galaxy Note 2 — Note 2 doesn't start anymore

Hi there,
I hope that somebody can help me.
My Galaxy Note 2 stopped working all of the sudden. It was running without any problems when it suddenly restarted without a reason. Since then it does not boot anymore, any attempt ends on the screen where it shows "Samsung Galaxy Note II GT-N7100". The only chance to switch it off after this is removing the battery. The phone was not rooted, it was running stock Android 4.3 before the crash.
Pressing Home and Volume-up during power-on doesn't show the menu so I'm not able to do a factory reset. Instead it shows the android robot and the text "Downloading... Do not turn off target!!"
I was hoping to have a chance to get a copy of the data of the internal memory so I followed the instructions to install the "Heimdall suite". When I start the phone in download mode (or what's left of it) I get the following responses to Heimdall commands:

C:\Note-2\Heimdall Suite>heimdall detect
Device detected


C:\Note-2\Heimdall Suite>heimdall print-pit

Initialising connection...
Detecting device...
Claiming interface...
Setting up interface...

Checking if protocol is initialised...
Protocol is not initialised.
Initialising protocol...
Handshaking with Loke...

Beginning session...
Session begun with device of type: 131072

Downloading device's PIT file...
ERROR: Failed to receive PIT file size!
ERROR: Failed to download PIT file!

To make sure my setup is correct I've tested it with with a working Galaxy S3 which doesn't give me the error messages after the second command.

Is there any way to get access to the data that is stored on the internal memory?
The phone is still under warranty so if there is a way to get access I'd prefer one that doesn't void the warranty...

Thank you very much for any hint!
Regards -- Markus