Server (lag?) Bug

When i'm playing on a server I always have a weird bug that will put me in "ghostmode" like this video: http://www.youtube.com/watch?v=6jQEf9YE8fE . I can walk, destroy, place etc. client-side but not server-side. I have to relog to go further but even then after a few seconds i'm trapped in "ghostmode". I think it's because of lag, but i'm not sure.