Your crash dumps are not showing adequate information about the crashes, still, I am suggesting you something.
Uninstall Avira. A stop 0x50 (as your case is) mostly occur for an Antivirus, and Avira is not a very trustworthy one. use Microsoft Security Essentials Download | Free Spyware Protection
The Latest version of nVidia is troublesome. Roll back to the earlier stable version.
As our crash dumps are not showing any finite probable cause. In such a situation, it is better to enable Driver Verifier to monitor the drivers. Driver Verifier - Enable and Disable
Run Driver Verifier for 24 hours or the occurrence of the next crash, whichever is earlier.
Let us know the results, with the subsequent crash dumps, if any.