I'm using laptop Acer Nitro VN7-571G-53N6, nvidia GeForce 840M. This is a screenshot of the error:
[11.128989] nouveau E[DEVICE][0000:03:00.0] unknown chipset, 0x118010a2 [11.129037] nouveau E[ DRM] failed to create 0x80000080, -22
As far as I can see the open source driver in this release doesn't support this relatively new card.
Did this happen with the live session or an actual installation?
A workaround in these scenarios for installations seems to be:
recovery modevia advanced options in GRUB.
Please test the latest LTS and non-LTS ISO images (currently 14.04.01 and 14.10). If the issue still exists on the latest non-LTS, then please file a bug. Here is an example for an older card:
Unfortunately, this error can be very misleading, while in most cases you get this after modifiyng UEFI settings and it has nothing to do with your nVidia chipset. In many cases its caused by an NTFS partition which was not completely unmounted. The solution can be turning the Fast startup off in Windows (http://www.eightforums.com/tutorials/6320-fast-startup-turn-off-windows-8-a.html).