Movement Bug

I was playing some ranked matches for fun, and every once in a while my character would stop moving and casting abilities. the movements i tried to issue while standing still cause my character to queue them up in order, meaning if i was prevented from moving, and i move clicked right, used summoner flash, and then use my ultimate, it would do those, however after 3 or 4 seconds. in my first match with this bug i was using Annie, however i rarely had the bug occur, however in my second game with Ziggs, it happened very often. i managed to record it happening with fraps. if anyone is interested the video will be bellow. If someone could help me fix the problem, or at least diagnoses it i would appreciate it very much. Bug video