Code:
BugCheck 9F, {3, fffffa8006ae6060, fffff80000b9c3d8, fffffa800934dd10}

*** WARNING: Unable to verify timestamp for nvlddmkm.sys
*** ERROR: Module load completed but symbols could not be loaded for nvlddmkm.sys
Probably caused by : nvlddmkm.sys
The bugcheck indicates that the device object has been holding a power-related IRP for too long.

Code:
0: kd> !irp fffffa800934dd10
Irp is active with 3 stacks 2 is current (= 0xfffffa800934de28)
 No Mdl: No System Buffer: Thread 00000000:  Irp stack trace.  
     cmd  flg cl Device   File     Completion-Context
 [  0, 0]   0  0 00000000 00000000 00000000-00000000    

            Args: 00000000 00000000 00000000 00000000
>[ 16, 2]   0 e1 fffffa8008273480 00000000 00000000-00000000    pending
           \Driver\nvlddmkm
            Args: 00016600 00000001 00000004 00000006
 [  0, 0]   0  0 00000000 00000000 00000000-fffffa8009143160    

            Args: 00000000 00000000 00000000 00000000
Code:
0: kd> !devobj fffffa8008273480 f
fffff80003282fb0: Unable to get value of ObpRootDirectoryObject
Device object (fffffa8008273480) is for:
 InfoMask field not found for _OBJECT_HEADER at fffffa8008273450
 \Driver\nvlddmkm DriverObject fffffa8008002620
Current Irp 00000000 RefCount 0 Type 00000023 Flags 00002004
DevExt fffffa80082735d0 DevObjExt fffffa8008273f88 
Characteristics (0x00000100)  FILE_DEVICE_SECURE_OPEN
Device queue is not busy.
----------------------------------------------------------------------------

Code:
0: kd> lmvm nvlddmkm
start             end                 module name
fffff880`056bb000 fffff880`061a0000   nvlddmkm T (no symbols)           
    Loaded symbol image file: nvlddmkm.sys
    Image path: nvlddmkm.sys
    Image name: nvlddmkm.sys
    Timestamp:        Fri Jun 21 10:06:16 2013 (51C41788)
    CheckSum:         00AB87FF
    ImageSize:        00AE5000
    Translations:     0000.04b0 0000.04e4 0409.04b0 0409.04e4
Please update your nVidia graphics card driver, to the latest WHQL version, following this method:

Version: 320.49
Release Date for Desktops and Notebooks : July 1st 2013
In Device Manager: 9.18.13.2049
  1. Start Type: Device Manager
  2. Expand Display Adapters
  3. Right-Click Driver Name, Uninstall
  4. Reboot
  5. Run Driver Sweeper
  6. Reboot
  7. Install Downloaded Driver

Driver Sweeper will scan for any left over files from the old driver, old driver files can cause conflicts with new driver installations. Create a System Restore point beforehand, in case any problems or issues arise.

Driver Sweeper: