@ Masters:
1. As this is done after halo has done its own rendering business I dont think theres a feasible way to exclude the hud.
2. I get that too when windowed, whenever winamp or something pops up to tell me something. I think its an external issue where halo's gamma gets overriden when it looses focus.
3. As with 1. changing things that happen in Halo's own rendering code isn't really feasible, but the bloom shader itself is easily alterable. One of the passes is a bright pass filter to pick out only the brightest areas, so changing that to include lower values may help to pick out the dynamic lights, but would also make everything else have more bloom.

@StankBacon:
Rename the shader_list and PP_MotionBlur files to something different (to disable post processing completely) and see if it loads as normal.