Brilliant detective work, and a great interpretation of the clues. BUt after reading the story it is still not fully clear as to if the actual fault was in software or in hardware, or in address assignment. Changing code was the fix, of course, but I am not sure that was the actual problem.
This sounds like a simple case of software debugging, not a particularly esoteric problem. I will add that there are all sorts of ongoing issues with PC sound. For example, when my Windows Vista machine goes to sleep, after it wakes up the sound system is down cause it can't see any of the hardware.
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