It happens to me in laggy zones once in a while. I usually remedy it by restarting my pc and if that doesn't work I pay closer attention to when my spells actually land and don't recast until maybe a second longer than usual. I also do a little twist to the side when I stop before I cast to make sure. The twisting before a cast is a trick a wizzy friend let me in on back in the kunark days. Anyway, hope I helped you.