I am having problems with my All-In-Wonder Radeon. In OpenGL, it's quite obvious that VSync is disabled. I get image tearing, etc. I can enable and disable it in ATi's control panel as much as I like, ...

I'm not sure about this, but is vsync tied to the refresh rate of your main monitor? In that case, everything would be waiting for a vertical sync, but it would come at the wrong time for the second ...