Seems the earlier reported Overclocking problem found in the latest WHQL Nvidia drivers was just an accident afterall, as NVidia has just released some new drivers (currently in Beta) that fix the issue.

New in Version 196.34

* Fixed a bug with v196.21 that prohibited GPU overclocking

Go check it out, they’ve got downloads for all versions of Windows.

via NVIDIA DRIVERS 196.34 BETA.