i noticed the engine enlight surface per polygon . it make the poly instantly enlight on wall of fortress and house when i approach with my torch drawn. quite strange, and because i know there is a [censored] huge number of mods, i 'm wondering if there is a mod to improve that.
i have OBGE v3 , with AO enabled, i tested all feature of this plugin , no one of these seems to be the problem.

i show you a video of that , when youtube finish to publish it ...
http://www.youtube.com/watch?v=dcW6_IJkoIA

It's a bug in Liquid Water.

Download the fix http://www.mediafire.com/?y9m2q1zf3m8pnx2 and recompile the appropriate shader (delete the PSO or VSO file that shares its name with the HLSL you downloaded and restart Oblivion with bCompileSources set to 1 in the OBGE.INI) to get rid of that.

thanks for this ultra fast answer.