U2515H Monitor "The current input timing is not supported by the monitor display"

Hi,

I just bought a U2515H.

I am running ubuntu 14.04, and since I changed the monitor, I have a black screen after boot saying ""The current input timing is not supported by the monitor display" and asking to use 2560x1440 at 60Hz.

I don't want to have the full 2560x1440 resolution on this computer, just a regular display would be good.

I want to use this monitor to plug also a laptop which works fine with the monitor.

I tried to plug the previous monitor, switch to the dell after logged in, but as soon as I "detect displays", the monitor will go off.

lshw:

*-core
description: Motherboard
product: ALiveXFire-eSATA2..
vendor: ASRock
physical id: 0
*-firmware
description: BIOS
vendor: American Megatrends Inc.
physical id: 0
version: P3.80
date: 03/26/2010
size: 64KiB
capacity: 448KiB
capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer int10video acpi usb ls120boot zipboot biosbootspecification

...

*-display
description: VGA compatible controller
product: G98 [GeForce 8400 GS Rev. 2]
vendor: NVIDIA Corporation
physical id: 0
bus info: pci@0000:02:00.0
version: a1
width: 64 bits
clock: 33MHz
capabilities: vga_controller bus_master cap_list rom
configuration: driver=nouveau latency=0
resources: irq:18