Laptop goes into suspend mode on bootup on a docking station with two external monitors.

I upgraded to Xubuntu v15.04 over the weekend.

Since then my laptop will not boot (goes into suspend mode), when connected to the docking station with two external monitors and the lid closed, or when not on docking station, but connected to an external monitor and the laptop lid is in closed state.

But if I start the laptop without any external monitor, or if the lid is open, then I could boot in, but could not extend the display to the external monitor.

From my /var/log/syslog, I got the following information:

[..snip..]
Apr 27 09:07:21 lap-0452 systemd[1]: Found device LVM PV spkRdx-u3i8-ot1F-4c0g-cbV6-REo5-Lg984M on /dev/dm-0.
Apr 27 09:07:21 lap-0452 systemd[1]: Created slice system-lvm2\x2dpvscan.slice.
Apr 27 09:07:21 lap-0452 systemd[1]: Starting system-lvm2\x2dpvscan.slice.
Apr 27 09:07:21 lap-0452 systemd[1]: Starting LVM2 PV scan on device 252:0...
Apr 27 09:07:21 lap-0452 systemd[1]: Started LVM2 PV scan on device 252:0.
Apr 27 09:07:21 lap-0452 systemd[1]: Found device ST9500423AS 1.
Apr 27 09:07:21 lap-0452 python3: io/hpmud/pp.c 627: unable to read device-id ret=-1
Apr 27 09:07:21 lap-0452 systemd-udevd[425]: worker [447] /devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.4/3-1.4.2/3-1.4.2.1 is taking a long time
Apr 27 09:07:21 lap-0452 systemd-udevd[425]: worker [459] /devices/pci0000:00/0000:00:1d.0/usb4/4-1/4-1.6 is taking a long time
Apr 27 09:07:21 lap-0452 systemd[1]: systemd-udev-settle.service start operation timed out. Terminating.
Apr 27 09:07:21 lap-0452 systemd[1]: Failed to start udev Wait for Complete Device Initialization.
Apr 27 09:07:21 lap-0452 systemd[1]: Unit systemd-udev-settle.service entered failed state.
Apr 27 09:07:21 lap-0452 systemd[1]: systemd-udev-settle.service failed.

[..snip..]

Apr 27 09:07:26 lap-0452 systemd[1]: Started Detect the available GPUs and deal with any system changes.
Apr 27 09:07:26 lap-0452 systemd[1]: Starting Light Display Manager...
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> init!
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> update_system_hostname
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> interface-parser: parsing file /etc/network/interfaces
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> interface-parser: finished parsing file /etc/network/interfaces
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> management mode: unmanaged
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> devices added (path: /sys/devices/pci0000:00/0000:00:19.0/net/eth0, iface: eth0)
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> device added (path: /sys/devices/pci0000:00/0000:00:19.0/net/eth0, iface: eth0): no ifupdown configuration found.
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> devices added (path: /sys/devices/pci0000:00/0000:00:1c.3/0000:25:00.0/net/wlan0, iface: wlan0)
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> device added (path: /sys/devices/pci0000:00/0000:00:1c.3/0000:25:00.0/net/wlan0, iface: wlan0): no ifupdown configuration found.
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> devices added (path: /sys/devices/virtual/net/lo, iface: lo)
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> device added (path: /sys/devices/virtual/net/lo, iface: lo): no ifupdown configuration found.
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> end _init.
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> Loaded plugin ifupdown: (C) 2008 Canonical Ltd. To report bugs please use the NetworkManager mailing list.
Apr 27 09:07:27 lap-0452 NetworkManager[987]: <info> Loaded plugin keyfile: (c) 2007 - 2013 Red Hat, Inc. To report bugs please use the NetworkManager mailing list.
Apr 27 09:07:27 lap-0452 kernel: [ 211.304035] done.
Apr 27 09:07:27 lap-0452 kernel: [ 211.304048] PM: Preparing system for mem sleep
Apr 27 09:07:45 lap-0452 kernel: [ 211.306778] Freezing user space processes ... (elapsed 0.156 seconds) done.
Apr 27 09:07:45 lap-0452 kernel: [ 211.462988] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
Apr 27 09:07:45 lap-0452 kernel: [ 211.464388] PM: Entering mem sleep
Apr 27 09:07:45 lap-0452 kernel: [ 211.464420] Suspending console(s) (use no_console_suspend to debug)
[..snip..]

I also made the following config changes, but they had no effect:
$ grep IgnoreLid /etc/UPower/UPower.conf
IgnoreLid=true

$ grep HandleLidSwitchDocked /etc/systemd/logind.conf
HandleLidSwitchDocked=ignore

Additional information:
Laptop: HP EliteBook 8560w
Display driver: NVIDIA binary driver - version 346.59 from nvidia-346 (proprietary, tested)
$ uname -a
Linux lap-0452 3.19.0-15-generic #15-Ubuntu SMP Thu Apr 16 23:32:37 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux