The Dell support page offers a few things to check, but says if all else fails, replace the video card.
Maybe replacing the video card is worth it to get rid of all the headaches.
THREAD STUCK IN DEVICE DRIVER
This Blue Screen error indicates that a device driver-almost always a video card driver-is stuck waiting for something (usually a hardware operation) to happen. Most of you have probably seennv4_disp.sys associated with this Blue Screen.
- Ensure the video drivers are updated to the latest Dell version.
- The system BIOS is fully up-to-date.
- If both the video driver and the system BIOS are fully up-to-date, check with the manufacturer for recent driver updates.
- As a last resort, try exchanging the video card.
Note: Reinstalling Windows is not likely to prevent this error from reoccurring.
http://www.dell.com/support/article/us/en/19/SLN129813/EN#Error6