Sound Dissapearing please help

Im having a major problem here which i cant seem to sort out…

After using cubase for a few minutes my sound dissapears. Meters are working etc but just no sound. I exit cubase, disable and reanable my sound card in sound options and the sound comes back for a short period again.

Im running Cubase elements 6 x64bit windows 7 with m-audio firewire 410 and a edirol pcr-m30. I have updated every driver i can think off, soundcard, graphics card, pcr, windows and ive even updated my bios to the latest version. i have the onboard sound card disabled in the bios also. its better if i have no midi controller connected. i have tried using my synthstation as a controller but i still get the same problem.

If anyone has any ideas i would be extremely gratefull as i’m desperate, thanks

EDIT I am now convinced it may be a usb driver conflict as it doesnt happen when my usb midi keyboard is disconnected, is there anyway i can check this?

Ok. I sorted this out the Only way possible which was to revert back to x86 version of cubase,its obvioisly some sort of conflict between cubase,m-audio drivers and usb drivers,i took all usb devices including the hub out of the equation and it was still a problem. I guess full x64 compatability is still way off. Be it due to steinberg,windows or third party drivers i dont know!!!