Sorry for gravedigging, but I have information to help fellow googlers
I had the same issue and asked in the official SEUS topic, here's the reply I got. (Posting here to help with people looking for answers)
Ok, the crazy bright screen is a common problem with a lot of shader packs that incorporate particular lighting modifications when used with mods that add blocks and materials to the game without any maps, resulting in the shader core not being able tell how to project light, shadows, reflections e.t.c. on to those items. Things like BuildCraft and ThermoCraft are known to be the most effected because of the blocks and the way they were designed, but sadly there isn't a fix for it. Either a large part of the shader needs to be deactivated, or the mods adding materials need to be tweaked to work with shaders.