The sound issue: The random / incorrect sound clips playing.
This problem typically manifests itself first as the voice clip "This would be faster with wings" playing during the opening sequence, followed by random sound clips playing during Demigod selection, and random sound clips being played during events in the match.
Installing from CD and doing the update now always causes this problem for me. (never did before)
To fix: download the game completely from impulse instead of installing from CD.
This is not a hardware problem or OS problem, it is a patch update problem in the script that sets the sound events in the Forge.fev file, possibly when installing from CD when your account thinks you have the digital download version. (the above mentioned file itself is fine during the patch process, and I have compared both the working and non working versions, which are identical)
Why this is not hardware
Never had this problem before using the same hardware, and I have tested it on multiple platforms that were working before to ensure the problem manifests after updating from a fresh CD install.
Why this is not OS
Never had this problem on various OSes before.
I also did a complete OS reinstall, and did other nerd stuff like monitor the ACIP APIC timer in bios that usually causes weird sound glitches. (these random clips are not caused by timer problems)
Hopefully this helps some of you who have been stuck with this problem.