Natty will not boot

[Curt Tresenriter]

On 12/9/2011 4:51 AM, Curt Tresenriter wrote:
> I just rebooted my Natty install and have it set to log me in w/o a 
> password but am presented with the chooser screen. I am the only user 
> and there is just one user account. Clicking on the acct. name looks 
> like it will give me the password field but it just loops back to the 
> login screen.
>
> What may have happened?
>
The only thing I see in dmesg are two messages repeated four times:
NVRM: failed to unregister from ACPI subsystem!
NVRM: failed to register with ACPI subsystem!

I think this may be the first reboot since the last updates, maybe 
something got broken?