This is not an NVIDIA bug, but instead the result of a recent patch for World of Warcraft to reduce mouse lag on slower computers by synchronizing the GPU(s). This change is unnecessary for NVIDIA users, and particularly for users with SLI configurations.

For optimal performance when playing World of Warcraft in SLI mode:

Disable vertical sync within the game's video options

Enable "hardware mouse acceleration" and disable "smooth mouse" within the game's video options

Note: "Smooth mouse" reduces mouse lag when the frame rate is low and "hardware mouse" is disabled