usually keep the cam below 3000 iso, maybe I accidentally hit the auto iso? I never notice this nasty blocky noise.

shot with my 1.4 25mm

Some ISO settings are bad to use, not sure which ones, but someone listed them once. You might have used a bad one. I know the odd numbers are supposed to be worse.

Stay in the middle row unless you go to a higher ISO, then switch to a lower. That's the ISO Bug in the GH2.

That looks like bug noise.

What film mode were you in. Nostalgic will bring out additional noise with the shadows.