08-19 is the oldest I have and 08-14 is the oldest on goo.
I suspect someone has hosted a copy here, but that's a big thread.
[ROM] Official CyanogenMod 9 Nightly Build Discussion - CyanogenMod [HP Touchpad] - RootzWiki
I'd create that backup and try a factory reset. You might have to reflash gApps after. See if that changes anything. If not, try the 8-14 build (or try that first).
I have the 09/03 nightly and my microphone works fine in Google Play Store.
