I am having the same problem, sometimes when I change theme it works fine again. Upon further investigation I can sum up either it is a bug in VWM, or error in coding within the config files of the theme (easy to fix). However it shouldn't be windows XP, because I have 98, 2000 and XP pro and I tried them all. Sometimes it happens and sometimes not, since it is not a big issue I just ignor it most of the time...