Not being familiar with LSH, I'm not sure that this is a relevant question, but have you applied the 4Gb patch? Are you on a desk top or laptop (GTX950 or 950M and DDR3 or DDR5)?
Also, Nvidia cards are a bit finicky about SH3. This is an old post, but the settings are still relevant.
http://www.subsim.com/radioroom/showthread.php?t=128517