Placing signs causes game to freeze

Playing a multiplayer world (this may or may not be relevant to the issue) and whenever I place a sign there is a 90% chance it will just freeze up and I will be unable to type anything or esc out of it, therefor meaning I have to close down the whole game. 

Does not happen every time but I have no way of knowing when it will happen so can't use signs for fear it will freeze.