v. 1.5.6 still have problem - if some gpus stop hashing the miner not hangs but just stoped and not showing any information further. So if i see that and press some key (space or h for example) it will show that gpu's hash speed is 0 and make reconnect to pool and after it will work good for some time.
my guess is its a missconfigured rig than the miner, for me even 1.3.* versions run rock solid