Hi,

I have the same problem in a Dell XPS15 L502X system. What I found is that after installing via "Additional drivers" the the module is not loaded neither found in the system with modprobe

root@ABequer:/dev# lsmod | grep nvidia
nvidia              10709116  0 
root@ABequer:/dev# modprobe nvidia
FATAL: Module nvidia not found.
root@ABequer:/dev#
root@ABequer:/dev# lspci -k
00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor Family DRAM Controller (rev 09)
	Subsystem: Dell Device 04b6
	Kernel driver in use: agpgart-intel
00:01.0 PCI bridge: Intel Corporation 2nd Generation Core Processor Family PCI Express Root Port (rev 09)
	Kernel driver in use: pcieport
	Kernel modules: shpchp
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
	Subsystem: Dell Device 04b6
	Kernel driver in use: i915
	Kernel modules: i915
00:16.0 Communication controller: Intel Corporation 6 Series Chipset Family MEI Controller #1 (rev 04)
	Subsystem: Dell Device 04b6
00:1a.0 USB Controller: Intel Corporation 6 Series Chipset Family USB Enhanced Host Controller #2 (rev 05)
	Subsystem: Dell Device 04b6
	Kernel driver in use: ehci_hcd
00:1b.0 Audio device: Intel Corporation 6 Series Chipset Family High Definition Audio Controller (rev 05)
	Subsystem: Dell Device 04b6
	Kernel driver in use: HDA Intel
	Kernel modules: snd-hda-intel
00:1c.0 PCI bridge: Intel Corporation 6 Series Chipset Family PCI Express Root Port 1 (rev b5)
	Kernel driver in use: pcieport
	Kernel modules: shpchp
00:1c.1 PCI bridge: Intel Corporation 6 Series Chipset Family PCI Express Root Port 2 (rev b5)
	Kernel driver in use: pcieport
	Kernel modules: shpchp
00:1c.3 PCI bridge: Intel Corporation 6 Series Chipset Family PCI Express Root Port 4 (rev b5)
	Kernel driver in use: pcieport
	Kernel modules: shpchp
00:1c.4 PCI bridge: Intel Corporation 6 Series Chipset Family PCI Express Root Port 5 (rev b5)
	Kernel driver in use: pcieport
	Kernel modules: shpchp
00:1c.5 PCI bridge: Intel Corporation 6 Series Chipset Family PCI Express Root Port 6 (rev b5)
	Kernel driver in use: pcieport
	Kernel modules: shpchp
00:1d.0 USB Controller: Intel Corporation 6 Series Chipset Family USB Enhanced Host Controller #1 (rev 05)
	Subsystem: Dell Device 04b6
	Kernel driver in use: ehci_hcd
00:1f.0 ISA bridge: Intel Corporation HM67 Express Chipset Family LPC Controller (rev 05)
	Subsystem: Dell Device 04b6
	Kernel modules: iTCO_wdt
00:1f.2 SATA controller: Intel Corporation 6 Series Chipset Family 6 port SATA AHCI Controller (rev 05)
	Subsystem: Dell Device 04b6
	Kernel driver in use: ahci
	Kernel modules: ahci
00:1f.3 SMBus: Intel Corporation 6 Series Chipset Family SMBus Controller (rev 05)
	Subsystem: Dell Device 04b6
	Kernel modules: i2c-i801
01:00.0 VGA compatible controller: nVidia Corporation Device 0df5 (rev a1)
	Subsystem: Dell Device 04b6
	Kernel driver in use: nvidia
	Kernel modules: nvidia-current, nouveau, nvidiafb
03:00.0 Network controller: Intel Corporation Centrino Wireless-N 1030 (rev 34)
	Subsystem: Intel Corporation Centrino Wireless-N 1030 BGN
	Kernel driver in use: iwlagn
	Kernel modules: iwlagn
04:00.0 USB Controller: NEC Corporation uPD720200 USB 3.0 Host Controller (rev 04)
	Subsystem: Dell Device 04b6
	Kernel driver in use: xhci_hcd
	Kernel modules: xhci-hcd
06:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 06)
	Subsystem: Dell Device 04b6
	Kernel driver in use: r8169
	Kernel modules: r8169
root@ABequer:/dev#