Mario Galaxy FPS drop for no reason (apparently)

[Shonumi]

@NV, Pauldachz - I doubt it's a CPU bottleneck. A stock 2500K shouldn't do so bad as to go down to 30 FPS. SMG under HLE audio isn't that CPU intensive. If you look at the screenshot in the OP, it's clear that the GPU is clocked extremely low (less than 300MHz!). It looks like it is idling.