sound cuts out at random...help!!!!!

[badandy85]

just got civ iv and patched it, all is ok except the sound. after playing for a while, its different each time, the sound just goes dead. when i drop back to windows i have no sound for anything, music, other games etc, until i restart my pc. i have no idea! have updated my drivers etc. using onboard sound AC'97. dont need a sound card as play loads of high end games with no problem. spec: 3000+ amd, 1gb 3200 ram, 5950 ultra 256mb, 200gb seagate hd. im new to this so any help would be great! cheers