Perhaps you can also try , some off the effects options in the config file.
If you do : Change ONLY one at a time , change it back and then try another.


Effects=1 ; you can try 0 , but that would prob negatively effect other things too
EffFlags.Light=1 ; this might be the one that you want to try 1st setting it to 0
EffFlags.SpriteRender=0 ; perhaps enable it ? to 1
EffFlags.LightSpritesProj=1 ; 2nd try would be this to 0
EffFlags.LightContextSprites=1 ; ? you can try 0 , but your guess is as good as mine.
EffFlags.SWLight=0 ; would leave this one at 0 , looks like software ligthts , this will probably be slow.