iPhone 4 sound issue please help

Hi experts, need some help.

I've had my iP4 for 2 years now, mostly trouble free.  Recently my sounds have "mostly" stopped working and I just can't figure out why.  I've done a lot of troubleshooting so here is what the symptoms are:

- Volume up/down buttons do not work, nothing happens when pressed

- Silent switch does not work, nothing happens when switched

- Lock sound does not happen

- Phone does not ring (only vibrates)

- Phone does not alert or chime

- Some apps audio does not work, but most apps play audio fine (youtube, music, videos, most games, etc)

- When selecting ring-tone or alert sounds I can hear the sound, so the speaker is working fine

Here is what I've tried

- check all settings and switches, certainly not a setting issue

- cleaned the dock connector with a brush, it is very clean

- cleaned headphone jack, and insert/remove headphones multiple times

- wiped all settings and restored to factory settings

- updated to latest ios6 firmware

- deleted "com.apple.iapd.plist" file using iexplorer, did nothing

Seems like I'm just about out of options now!  Thanks for any help.