Comment 19 for bug 522328

This happened to me too, with geforce 9500m on lucid 64 bit. Oddly it would happpen some of the times. but not all of them. I found a workaround which might work for you too.

The messages in my kern.log say:

May 20 01:29:52 aku kernel: [ 1613.675079] ACPI: PCI Interrupt Link [LPMU] enabled at IRQ 23
May 20 01:29:52 aku kernel: [ 1613.675084] nvidia 0000:00:03.5: PCI INT B -> Link[LPMU] -> GSI 23 (level, low) -> IRQ 23
May 20 01:29:52 aku kernel: [ 1613.675110] nvidia 0000:02:00.0: enabling device (0000 -> 0003)
May 20 01:29:52 aku kernel: [ 1613.675120] nvidia 0000:02:00.0: PCI INT A -> Link[Z00Q] -> GSI 23 (level, low) -> IRQ 23
May 20 01:29:52 aku kernel: [ 1613.675144] vgaarb: device changed decodes: PCI:0000:02:00.0,olddecodes=io+mem,decodes=nonew ns=none
May 20 01:29:52 aku kernel: [ 1613.675422] NVRM: The NVIDIA probe routine was not called for 1 device(s).
May 20 01:29:52 aku kernel: [ 1613.675424] NVRM: This can occur when a driver such as rivafb, nvidiafb or
May 20 01:29:52 aku kernel: [ 1613.675425] NVRM: rivatv was loaded and obtained ownership of the NVIDIA
May 20 01:29:52 aku kernel: [ 1613.675425] NVRM: device(s).
May 20 01:29:52 aku kernel: [ 1613.675427] NVRM: Try unloading the rivafb, nvidiafb or rivatv kernel module
May 20 01:29:52 aku kernel: [ 1613.675428] NVRM: (and/or reconfigure your kernel without rivafb/nvidiafb
May 20 01:29:52 aku kernel: [ 1613.675429] NVRM: support), then try loading the NVIDIA kernel module again.
May 20 01:29:52 aku kernel: [ 1613.675431] NVRM: loading NVIDIA UNIX x86_64 Kernel Module 195.36.15 Fri Mar 12 00:29:13 PST 2010
May 20 01:30:12 aku kernel: Kernel logging (proc) stopped.

I think the problem is that for the sake of plymouth, ubuntu loads the vga16fb module before it loads the nvidia module. I solved it using the following workaround, which regrettably diables plymouth for nvidia folks:

sudo gedit /etc/modprobe.d/blacklist.conf

add the following lines to the end of the file:

#Block modules messing with nvidia
blacklist vga16fb
blacklist nouveau
blacklist rivafb
blacklist nvidiafb
blacklist rivatv