umm.. ur using LSTS to switch themes? if that's the case then some themes don't have *.thm file included and that confuses LSTS. That *.thm file should be in the theme's dir. u can use LSTS to make one ;)

if that's not the case then some themes just aren't OTS compatible and need some major tweaking before actually using them. be sure to read the readme file before switching!