Lose sound and need to reboot

i just hook'd up an optical cable from my computer to a receiver and enabled my digital sound. plays music fine but when i play call of duty for a certain amount of time the sound cuts off and i need to reboot to get it back. i download'd all the current drivers from realtek and nothing seems to fix this. what can it be?
 
its not that, i have temp sensors throughout and they set to beep at a certain temp, nothing has gone off, but that doesn't mean its not run'n hot. but wait there's more...after my sound goes when i open media player it runs real slow, like a second equals 2 seconds if that makes sense to you (every second that goes by in media player, equals at least 2 or more seconds real time). but that over heat'n thing would be crazy, i got 4 fans run'n at 1700-1800 all the time, i'll monitor the temps to see...i read somewhere that the "i" series intel chips have problems transmitting audio, has anyone heard this?
 
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