Re: nvidia-setting and glxgears
This is not puzzling, it is logical.
There are 2 ways to set the sync to vblank:
1. nvidia-setting's opengl options
2. compiz settings panel
These 2 might have a conflict if only one of them is set. It is not a problem per se, but you wont know when it is enabled and when its not. Launching nvidia-settings probably set it to enabled that is the default setting AFAIK.
Always set both to the same setting to control it.