To resolve this issue use the parameters "x-systemd.automount" and "cache=none" in the share to be mounted using fstab.
Example:
//192.168.56.1/Data/DEV/ /home/brlight/DEV/ cifs auto,x-systemd.automount,cache=none,users,username=eduardo,password=questor 0 0
I'm not sure about that, but it seems that this problem occurs for two reasons: 1 - The network is unavailable when the system tries to mount the share; 2 - When you using the parameter "x-systemd.automount", the UI (KDE) try to mount the share when needed or inherits some kind of permission to mount the share!
I appreciate comments and possible corrections!
Thanks to kaipee!
Source: https://bbs.archlinux.org/viewtopic.php?pid=1168782