Many thanks for the replies, A major reason for posting for help is it does wonders for ones own reasoning and sugestions arising almost alwasy helps. A couple of points. The hardware is all higher end items, the pSu for instance being a Corsair AX760 and the power consumed is WELL within the limits of this PSU. The reason for the Radeon 7870 is I do a lot of development work on 3D animated graphics (I am developing a train simulator) and good mesa3d performance is mandatory. The problem is almost certainly something to do with the GPU as as stated the sound does keep playing so what is happenning is an xserver display lockup and the kernel is still running (Note it appears the X app concerned vlc is still running.. My own thinking is Craig has hit the nail firmly on the head, although I have run the 7870 extensively on i386 with little trouble (Note I have actaully struck this before, an AMD card giving problems under certain versions of linux). I believe the way forward also is for an Nvidia card. I have tried both AMD and Nvidia offerings and from all this experience the Nvidia's with the closed source driver is superior. I do compile my own kernels, this machine (I am writing this on the AMD64 installed machine) is 3.16.7 compiled last november so its due for an update. Note also I have tried updating the kernel, it did not help. I do like to support AMD as the are at least trying to do something for Linux, but I have found there closed src driver 2D performce to be completely ____PATHETIC____ to say the least, mind you its now two or more years since I tried it last. I give a look at digging up a reasonable Nvidia card, a real high end job is a waste of money though. Lindsay