well, as u could have read in thousands of other posts (hint, hint!!), ls doesn't support multi-monitor systems. it can be adjusted to work with mm, but in a really crappy way. if u want to find information about adjusting your themes to display correctly on mm systems, search these forums. there are tons of threads about that.
i have heard rumours that if ls is going to support multi-monitoring, it's going to happen in the next version (that would be 0.25.x). until then u probably have get along with the old and rather annoying way.