They are using the most common exploit in the game- the old F1 trick. Basically, they're logging out and logging back in again quickly. You should find out if this server has a website, and report the ruffians- on most servers, using that is a bannable offense. If they won't ban them... go somewhere else- server ops who know what they're doing won't put up with that kind've behavior

Except they are warping out to a diffrent position and not simply disapearing and reaporign with slight movement

My advice is still the same- whatever they're doing is a bannable offense. Take it up with the Admins of the server you play on, or find another server

It turns out after Admin intervention that they can open internet explorer in a way that does it. They are reinstallign windows now.