Avrdude can't open port to program board - User permissions set correctly


I'm currently experiencing trouble programming a new Leonardo Ethernet board as trying to program it gives:

Arduino: 1.6.7 (Linux), Board: "Arduino Leonardo"

avrdude: Version 6.1, compiled on Dec 9 2015 at 13:04:00 Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/ Copyright (c) 2007-2014 Joerg Wunsch

System wide configuration file is "/usr/share/arduino/hardware/tools/avr/etc/avrdude.conf" User configuration file is "/home/manuel/.avrduderc" User configuration file does not exist or is not a regular file, skipping

Using Port : /dev/ttyACM0 Using Programmer : avr109 Overriding Baud Rate : 57600 avrdude: ser_open(): can't open device "/dev/ttyACM0": Permission denied

avrdude done. Thank you.

I'm using Arch Linux 4.3.3-3, avrdude 6.1, version 1.6.7 of the IDE and have previously used the current system to successfully program Unos, although I can't retry to program one until Monday.

While experimenting, I've noted that I'm able to program the board if running the IDE with root permissions. I tried programming the following:

void setup() {
  // put your setup code here, to run once:

void loop() {
  // put your main code here, to run repeatedly:

Using it, I can successfully send characters and receive their ASCII value through the Serial Monitor without using root permissions. Therefore the system is correctly configured to communicate with the board, however I'm not capable of programming it without root permissions.

I know I can simply use the IDE with root permissions and go around problem but this is really getting under my skin as I'm certain it used to work without them.

Any ideas?

(same here, avrdude: 6.3 ArchLinux arduino: 1.6.8

Due works fine.. )