Can't program arduino leonardo (Ubuntu 14.04 64bit, USB available)

Some days ago I bought a Arduino Leonardo board. I tried to get it running under Ubuntu (version 14.04 64bit), but so far I did not succeed.
I tried out several USB ports (both USB2, USB2 with additional HUB and USB3), used different USB cables but everything I tried ended up in the error log shown below.
I see the LED blinking (Pin 13), so I assume a boot loader is running. Monitoring "/dev/ttyACM1" gives me several "TEST OK"s, so I think the connection to the Leonardo board is established.

Is there someone outside who can give me a hint how I can debug further?

Sketch uses 4,252 bytes (14%) of program storage space. Maximum is 28,672 bytes.
Global variables use 151 bytes (5%) of dynamic memory, leaving 2,409 bytes for local variables. Maximum is 2,560 bytes.
Forcing reset using 1200bps open/close on port /dev/ttyACM1
PORTS {/dev/ttyACM1, /dev/ttyS0, } / {/dev/ttyACM1, /dev/ttyS0, } => {}
PORTS {/dev/ttyACM1, /dev/ttyS0, } / {/dev/ttyACM1, /dev/ttyS0, } => {}
Uploading using selected port: /dev/ttyACM1
/usr/arduino-1.7.8-linux64/hardware/tools/avr/bin/avrdude -C/usr/arduino-1.7.8-linux64/hardware/tools/avr/etc/avrdude.conf -v -patmega32u4 -cavr109 -P/dev/ttyACM1 -b57600 -D -Uflash:w:/tmp/build7364879576418150895.tmp/sketch_dec08a.cpp.hex:i 

avrdude: Version 6.0.1, compiled on Jan 15 2015 at 13:12:29
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "/usr/arduino-1.7.8-linux64/hardware/tools/avr/etc/avrdude.conf"
         User configuration file is "/root/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/ttyACM1
         Using Programmer              : avr109
         Overriding Baud Rate          : 57600
         AVR Part                      : ATmega32U4
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PA0
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65    20     4    0 no       1024    4      0  9000  9000 0x00 0x00
           flash         65     6   128    0 yes     32768  128    256  4500  4500 0x00 0x00
           lfuse          0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
           lock           0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00

         Programmer Type : butterfly
         Description     : Atmel AppNote AVR109 Boot Loader

Connecting to programmer: .
Found programmer: Id = "TEST OK"; type =  
    Software Version = T.E; Hardware Version = S.T
avrdude: error: buffered memory access not supported. Maybe it isn't
a butterfly/AVR109 but a AVR910 device?
Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

http://forum.arduino.cc/index.php?topic=267001.15